Network Working S.E. Kille
Group Isode Ltd.
INTERNET-DRAFT February 1997
Expires: August 1997
File: draft-kille-mixer-rfc1327bis-04.txt
MIXER (Mime Internet X.400 Enhanced Relay):
Mapping between X.400 and RFC 822/MIME
Status of this Memo
This document is an Internet Draft. Internet Drafts are working
documents of the Internet Engineering Task Force (IETF), its Areas,
and its Working Groups. Note that other groups may also distribute
working documents as Internet Drafts. Internet Drafts are draft
documents valid for a maximum of six months. Internet Drafts may be
updated, replaced, or obsoleted by other documents at any time. It is
not appropriate to use Internet Drafts as reference material or to
cite them other than as a ``working draft'' or ``work in progress.''
Please check the I-D abstract listing contained in each Internet Draft
directory to learn the current status of this or any other Internet
Draft.
Network Working Group S.E. Kille
Internet Draft Isode Ltd.
RFC 1327bis February 1997
Obsoletes: RFCs 987, 1026, 1138, 1148, 1327, 1495
Updates: RFC 822
MIXER (Mime Internet X.400 Enhanced Relay):
Mapping between X.400 and RFC 822/MIME
Status of this Memo:
This document describes a set of mappings which will enable
interworking between systems operating the CCITT X.400
Recommendations on Message Handling Systems (1984, 1988 and
1992 versions) / ISO IEC 10021 Message Oriented Text
Interchange Systems (MOTIS) [1,13,15], and systems using the
RFC 822 mail protocol [16] or protocols derived from RFC
822, supplemented by the MIME specifications [9]. Older
systems which do not use MIME are still supported. The
approach aims to maximise the services offered across the
boundary, whilst not requiring unduly complex mappings. The
mappings should not require any changes to end systems. This
document is a revision based on the evolving sequence of
RFCs 987, 1026, 1138, 1148 and 1327 [17-21], which it
obsoletes. It incorporates changes specified in RFC 1495
[4], which it also obsoletes.
This document specifies a mapping between two families of
protocols, which includes both protocol/service mappings and
use of a mandatory global mappings. This specification
should be used when this mapping is performed.
This draft document will be submitted to the RFC editor as
a protocol specification. Distribution of this memo is
unlimited. Please send comments to the WG mailing list
<ietf-mixer@innosoft.com>.
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Table of Contents
1 - Overview ...................................... 6
1.1 - X.400 ......................................... 6
1.2 - RFC 822 and MIME .............................. 6
1.3 - The need for conversion ....................... 7
1.4 - General approach .............................. 7
1.5 - Gatewaying Model .............................. 8
1.6 - Support of X.400 (1984) ....................... 11
1.7 - X.400 (1992) .................................. 12
1.8 - MIME .......................................... 12
1.9 - Body Parts .................................... 12
1.10 - Local and Global Scenarios ................... 13
1.11 - Compatibility with previous versions ......... 14
1.12 - Aspects not covered .......................... 14
1.13 - Subsetting ................................... 14
1.14 - Specification Language ....................... 15
1.15 - Related Specifications ....................... 15
1.16 - Document Structure ........................... 15
1.17 - Acknowledgements ............................. 16
2 - Service Elements .............................. 18
2.1 - The Notion of Service Across a Gateway ........ 18
2.2 - RFC 822 ....................................... 19
2.3 - X.400 ......................................... 23
3 - Basic Mappings ................................ 34
3.1 - Notation ...................................... 34
3.2 - ASCII and IA5 ................................. 36
3.3 - Standard Types ................................ 36
3.4 - Encoding ASCII in Printable String ............ 40
3.5 - RFC 1522 ...................................... 41
4 - Addressing and Message IDs .................... 43
4.1 - A textual representation of MTS.ORAddress ..... 44
4.2 - Global Address Mapping ........................ 52
4.3 - EBNF.822-address <-> MTS.ORAddress ............ 56
4.4 - Repeated Mappings ............................. 69
4.5 - Directory Names ............................... 72
4.6 - MTS Mappings .................................. 72
4.7 - IPMS Mappings ................................. 77
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5 - Detailed Mappings ............................. 83
5.1 - RFC 822 -> X.400: Detailed Mappings ........... 83
5.2 - Return of Contents ............................ 100
5.3 - X.400 -> RFC 822: Detailed Mappings ........... 100
Appendix A - Mappings Specific to SMTP ..................... 135
1 - Probes ........................................ 135
2 - Long Lines .................................... 135
3 - SMTP Extensions ............................... 135
3.1 - SMTP Extension mapping to X.400 ............... 135
3.2 - X.400 Mapping to SMTP Extensions .............. 136
Appendix B - Mapping with X.400(1984) ................. 138
Appendix C - RFC 822 Extensions for X.400 access ........... 140
Appendix D - Object Identifier Assignment .................. 141
Appendix E - BNF Summary ................................... 142
Appendix F - Text format for MCGAM distribution ............ 152
1 - Text Formats .................................. 152
2 - Mechanisms to register and to distribute
MCGAMs ..................................................... 152
3 - Syntax Definitions ............................ 153
4 - Table Lookups ................................. 154
5 - Domain -> OR Address MCGAM format ............. 155
6 - OR Address -> Domain MCGAM format ............. 155
7 - Domain -> OR Address of Preferred Gateway
table ...................................................... 156
8 - OR Addresss -> domain of Preferred Gateway
table ...................................................... 156
Appendix G - Conformance ................................... 157
Appendix H - Change History: RFC 987, 1026, 1138, 1148
............................................................ 159
1 - Introduction .................................. 159
2 - Service Elements .............................. 159
3 - Basic Mappings ................................ 160
4 - Addressing .................................... 160
5 - Detailed Mappings ............................. 160
6 - Appendices .................................... 161
Appendix I - Change History: RFC 1148 to RFC 1327 .......... 162
1 - General ....................................... 162
2 - Basic Mappings ................................ 162
3 - Addressing .................................... 162
4 - Detailed Mappings ............................. 163
5 - Appendices .................................... 163
Appendix J - Change History: RFC 1327 to this Document
............................................................ 164
1 - General ....................................... 164
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2 - Service Elements .............................. 164
3 - Basic Mappings ................................ 164
4 - Addressing .................................... 164
5 - Detailed Mappings ............................. 165
6 - Appendices .................................... 165
Appendix L - ASN.1 Summary ............................ 167
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Chapter 1 -- Overview
1.1. X.400
This document relates primarily to the ITU-T 1988 and 1992 X.400
Series Recommendations / ISO IEC 10021 International Standard.
This ISO/ITU-T standard is referred to in this document as
"X.400", which is a convenient shorthand. Any reference to the
1984 Recommendations will be explicit. Any mappings relating to
elements which are in the 1992 version and not in the 1988
version will be noted explicitly. X.400 defines an Interpersonal
Messaging System (IPMS), making use of a store and forward
Message Transfer System. This document relates to the IPMS, and
not to wider application of X.400, such as EDI as defined in
X.435.
1.2. RFC 822 and MIME
RFC 822 evolved as a messaging standard on the DARPA (the US
Defense Advanced Research Projects Agency) Internet. RFC 822
specifies an end to end message format, consisting of a header
and an unstructured text body. MIME (Multipurpose Internet Mail
Extensions) specifies a structured message body format for use
with RFC 822. The term "RFC 822" is used in this document to
refer to the combination of MIME and RFC 822. RFC 822 and MIME
are used in conjunction with a number of different message
transfer protocol environments. The core of the MIXER
specification is designed to work with any supporting message
transfer protocol.
One transfer protocol, SMTP, is of particular importance and
is covered in MIXER. On the Internet and other TCP/IP networks,
RFC 822 is used in conjunction with
RFC 821, also known as Simple Mail Transfer Protocol (SMTP)
[30], in a manner conformant with the host requirements
specification [10]. Use of MIXER with SMTP is defined in
Appendix A.
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1.3. The need for conversion
There is a large community using RFC 822 based protocols for mail
services, who will wish to communicate with users of the IPMS
provided by X.400 systems. This will also be a requirement in
cases where communities intend to make a transition between the
different technologies, as conversion will be needed to ensure a
smooth service transition. It is expected that there will be
more than one gateway, and this specification will enable them to
behave in a consistent manner. Note that the term gateway is
used to describe a component performing the mapping between RFC
822 and X.400. This is standard usage amongst mail implementors,
but differs from that used by transport and network service
implementors.
Consistency between gateways is desirable to provide:
1. Consistent service to users.
2. The best service in cases where a message passes through
multiple gateways.
1.4. General approach
There are a number of basic principles underlying the details of
the specification. These principles are goals, and are not
achieved in all aspects of the specification.
1. The specification should be pragmatic. There should not be
a requirement for complex mappings for "Academic" reasons.
Complex mappings should not be required to support trivial
additional functionality.
2. Subject to 1), functionality across a gateway should be as
high as possible.
3. It is always a bad idea to lose information as a result of
any transformation. Hence, it is a bad idea for a gateway
to discard information in the objects it processes. This
includes requested services which cannot be fully mapped.
4. Mail gateways operate at a level above the layer on which
they perform mappings. This implies that the gateway shall
not only be cognisant of the semantics of objects at the
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gateway level, but also be cognisant of higher level
semantics. If meaningful transformation of the objects that
the gateway operates on is to occur, then the gateway needs
to understand more than the objects themselves.
5. Subject to 1), the mapping should be reversible. That is, a
double transformation should bring you back to where you
started.
1.5. Gatewaying Model
1.5.1. X.400
X.400 defines the IPMS Abstract Service in X.420 , [11] which
comprises of three basic services:
1. Origination
2. Reception
3. Management
Management is a local interaction between the user and the IPMS,
and is therefore not relevant to gatewaying. The first two
services consist of operations to originate and receive the
following two objects:
1. IPM (Interpersonal Message). This has two components: a
heading, and a body. The body is structured as a sequence
of body parts, which may be basic components (e.g., IA5
text, or G3 fax), or forwarded Interpersonal Messages. The
heading consists of fields containing end to end user
information, such as subject, primary recipients (To:), and
importance.
2. IPN (Inter Personal Notification). A notification about
receipt of a given IPM at the UA level.
The Origination service also allows for origination of a probe,
which is an object to test whether a given IPM could be correctly
received.
The Reception service also allows for receipt of Delivery Reports
(DR), which indicate delivery success or failure.
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These IPMS Services utilise the Message Transfer System
(MTS) Abstract Service [12]. The MTS Abstract Service provides
the following three basic services:
1. Submission (used by IPMS Origination)
2. Delivery (used by IPMS Reception)
3. Administration (used by IPMS Management)
Administration is a local issue, and so does not affect this
standard. Submission and delivery relate primarily to the MTS
Message (comprising Envelope and Content), which carries an IPM
or IPN (or other uninterpreted contents). The Envelope includes
a message identifier, an originator, and a list of recipients.
Submission also includes the probe service, which supports the
MTS Probe. Delivery also includes Reports, which indicate whether
a given MTS Message has been delivered or not (or for a probe if
delivery would have happened).
The MTS is provided by MTAs which interact using the MTA
(Message Transfer Agent) Service, which defines the interaction
between MTAs, along with the procedures for distributed
operation. This service provides for transfer of MTS Messages,
Probes, and Reports.
1.5.2. RFC 822
RFC 822 is based on the assumption that there is an underlying
service, which is here called the 822-MTS service. The 822-MTS
service provides three basic functions:
1. Identification of a list of recipients.
2. Identification of an error return address.
3. Transfer of an RFC 822 message.
It is possible to achieve 2) within the RFC 822 header.
This specification will be used most commonly with SMTP as
the 822-MTS service. The core MIXER specification is written so
that it does not rely on non-basic 822-MTS services. Use of
non-basic SMTP services is described in Appendix A. The core of
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this document is written using SMTP terminology for 822-MTS
services.
An RFC 822 message consists of a header, and content which
is uninterpreted ASCII text. The header is divided into fields,
which are the protocol elements. Most of these fields are
analogous to IPM heading fields, although some are analogous to
MTS Service Elements or MTA Service Elements.
RFC 822 supports delivery status notifications by use of the
NOTARY mechanisms [28].
1.5.3. The Gateway
Given this functional description of the two services, the
functional nature of a gateway can now be considered. It would
be elegant to consider the SMTP (822-MTS) service mapping onto
the MTS Service Elements and RFC 822 mapping onto an IPM, but
there is a not a clear match between these services. Another
elegant approach would be to treat this document as the
definition of an X.400 Access Unit (AU). In this case, the
abstraction level is too high, and some necessary mapping
function is lost. It is necessary to consider that the IPM
format definition, the IPMS Service Elements, the MTS Service
Elements, and MTA Service Elements on one side are mapped into
RFC 822 + SMTP on the other in a slightly tangled manner. The
details of the tangle will be made clear in Chapter 5. Access to
the MTA Service Elements is minimised.
The following basic mappings are thus defined. When going
from RFC 822 to X.400, an RFC 822 message and the associated SMTP
information is always mapped into an IPM (MTA, MTS, and IPMS
Services) and a Delivery Status Notification is mapped onto a
Report. Going from X.400 to RFC 822, an RFC 822 message and the
associated SMTP information may be derived from:
1. An IPN (MTA, MTS, and IPMS services)
2. An IPM (MTA, MTS, and IPMS services)
A Report (MTA, and MTS Services) is mapped onto a delivery status
notification.
Probes (MTA Service) shall be processed by the gateway, as
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discussed in Chapter 5. MTS Messages containing Content Types
other than those defined by the IPMS are not mapped by the
gateway, and shall be rejected at the gateway if no other
gatewaying procedure is defined.
This specification is concerned with X.400 IPMS. Future
specifications may defined mappings for other X.400 content
types.
1.5.4. Repeated Mappings
The primary goal of this specification is to support single
mappings, so that X.400 and RFC 822 users can communicate with
maximum functionality.
The mappings specified here are designed to work where a
message traverses multiple times between X.400 and RFC 822. This
is often essential, particularly in the case of distribution
lists. However, in general, this will lead to a level of service
which is the lowest common denominator (approximately the
services offered by RFC 822).
Some RFC 822 networks may wish to use X.400 as an
interconnection mechanism (typically for policy reasons), and
this is fully supported.
Where an X.400 message transfers to RFC 822 and then back to
X.400, there is no expectation of X.400 services which do not
have an equivalent service in standard RFC 822 being preserved -
although this may be possible in some cases.
1.6. Support of X.400 (1984)
The MIXER definition is based on the initial specification of RFC
987 and in its addendum RFC 1026, which defined a mapping between
X.400(1984) and RFC 822. The core MIXER mapping is defined using
the full 1988 version of X.400, and not to a 1984 compatible
subset. New features of X.400(1988) can be used to provide a much
cleaner mapping than that defined in RFC 987. To interwork with
1984 systems, Appendix B shall be followed.
If a message is being transferred to an X.400(1984) system
by way of X.400(1988) MTA it will give a slightly better service
to follow the rules of Appendix B, than to downgrade without this
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knowledge. Downgrading specifications which supplement those
specified in X.400 (X.419) are given in RFC 1328[22] and RFC 1496
(HARPOON) [5].
1.7. X.400 (1992)
X.400 (1992) features are not used by the core of this mapping,
and so there is not an equivalent downgrade problem.
1.8. MIME
MIME format messages are generated by this mapping. As MIME
messages are fully RFC 822 compliant, this will not cause
problems with systems which are not MIME capable.
1.9. Body Parts
MIME and X.400 IPMS can both carry arbitrary body parts. MIME
defines a mechanism for adding new body parts, and new body parts
are registered with the IANA. X.400 defines a mechanism adding
new body parts, usually referred to as Body Part 15. Extensions
are defined by Object Identifiers, so there is no requirement for
a central body part registration authority. The Electronic
Messaging Association (EMA) maintains a list of some commonly
used body parts. The EMA has specified a mechanism to use the
File Transfer Body Part (FTBP) as a more generic means to support
message attachments. This approach is gaining widespread
commercial support.
The mapping between X.400 and MIME body parts is defined in
the companion MIXER specification, referenced here as RFC 1494bis
[8]. This document is an update of RFC 1494 [6].
Editor's Note:
References to 1494bis will be resolved as these two
documents are expected to progress in parallel.
These two specifications together form the complete MIXER
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Mapping.
1.10. Local and Global Scenarios
There are two basic scenarios for X.400/MIME interworking:
Global Scenario
There are two global mail networks (Internet/MIME and
X.400), interconnected by multiple gateways. Objects may
be transferred over multiple gateways, and so it is
important that gateways behave in a coherent fashion.
MIXER is critical to support this scenario.
Local Scenario
A gateway is used to connect a closed community to a global
mail network (this could be enforced by connectivity or
gateway authorisation policy). This is a common commercial
scenario. MIXER is useful to support this scenario, as it
allows an industry standard provision of service, but this
could be supported by something which was MIXER-like.
A solution for the global scenario will work for the local
scenario. However, there are aspects of MIXER which have
significant implementation or deployment effort (the global
mapping is the major one, but there are other details too) which
and are needed to support the global scenario, but are not needed
in the local scenario.
Note that the local scenario may be the driving force for
most deployments, and support of the global scenario may be an
important secondary goal.
There is also a transition effect. Gateways which are
initially deployed in a strict local scenario situation start to
find themselves in a global scenario. A common case is ADMD
provided gateways, which are targeted strictly at the local
scenario. In practice they soon start to operate in the global
scenario, because of distribution lists and messages exchanged
with X.400 users that are not customers of the ADMD. At this
point, users are hurt by the restrictions of a local scenario
gateway.
Note that conformance to MIXER applies to an instantiation
of a gateway, not just an implementation (although clearly it is
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critical that the implementation is capable of being operated in
a conformant manner).
MIXER's conformance target is the global scenario, and the
specification of MIXER defines operation in this way.
1.11. Compatibility with previous versions
The changes between this and older versions of the document are
given in Appendices H, I and J. These are RFCs 987, 1026,
1138, 1148 and 1327. This document is a revision of RFC 1327
[21]. As far as possible, changes have been made in a compatible
fashion.
1.12. Aspects not covered
There have been a number of cases where previous versions of this
document were used in a manner which was not intended. This
section is to make clear some limitations of scope. In
particular, this specification does not specify:
- Extensions of RFC 822 to provide access to all X.400
services
- X.400 user interface definition
These are really coupled. To map the X.400 services, this
specification defines a number of extensions to RFC 822. As a
side effect, these give the 822 user access to SOME X.400
services. However, the aim on the RFC 822 side is to preserve
current service, and it is intentional that access is not given
to all X.400 services. Thus, it will be a poor choice for X.400
implementors to use MIXER as an interface - there are too many
aspects of X.400 which cannot be accessed through it. If a text
interface is desired, a specification targeted at X.400, without
RFC 822 restrictions, would be more appropriate. Some optional
and limited extensions in this area have proved useful, and are
defined in Appendix C.
1.13. Subsetting
This proposal specifies a mapping which is appropriate to
preserve services in existing RFC 822 communities.
Implementations and specifications which subset this
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specification are non-conformant and strongly discouraged.
1.14. Specification Language
ISO and Internet standards have clear definitions as to the style
of language used. This specification maps between ISO/ITU-T
protocol and Internet protocols. This document uses ISO
terminology for the following reasons:
1. This was done in previous versions.
2. ISO language may be mechanically converted to Internet
language, but not vice versa.
The key elements of the ISO rules are:
1. All mandatory features shall clearly be indicated by
imperative statements or the word "shall" or "shall not".
2. Optional features shall be indicated by the word "may".
3. The word "should" and the phrase "may not" shall not be
used.
In some cases the specification issues guidance on use of
optional features, by use of the the phrase word "recommended" or
"not recommended".
To interpet this document according to Internet rules, replace
every occurrence of "shall" with "must".
1.15. Related Specifications
Mappings between Mail-11 and X.400 and Mail-11 and rfc822 are
described in RFC1405, using mappings related to those defined
here [2].
1.16. Document Structure
This document has five chapters:
1. Overview - this chapter.
2. Service Elements - This describes the (end user) services
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mapped by a gateway.
3. Basic mappings - This describes some basic notation used in
Chapters 3-5, the mappings between character sets, and some
fundamental protocol elements.
4. Addressing - This considers the mapping between X.400 OR
names and RFC 822 addresses, which is a fundamental gateway
component.
5. Detailed Mappings - This describes the details of all other
mappings.
There are also ten appendices.
WARNING:
THE REMAINDER OF THIS SPECIFICATION IS TECHNICALLY DETAILED.
IT WILL NOT MAKE SENSE, EXCEPT IN THE CONTEXT OF RFC 822 AND
X.400 (1988). DO NOT ATTEMPT TO READ THIS DOCUMENT UNLESS
YOU ARE FAMILIAR WITH THESE SPECIFICATIONS.
1.17. Acknowledgements
The work in this specification was substantially based on RFC 987
and RFC 1148, which had input from many people, who are credited
in the respective documents.
A number of comments from people on RFC 1148 lead to RFC
1327. In particular, there were comments and suggestions from:
Maurice Abraham (HP); Harald Alvestrand (Sintef); Peter Cowen
(X-Tel); Jim Craigie (JNT); Ella Gardner (MITRE); Christian
Huitema (Inria); Erik Huizer (SURFnet); Neil Jones (DEC); Ignacio
Martinez (IRIS); Julian Onions (X-Tel); Simon Poole (SWITCH);
Clive Roberts (Data General); Pete Vanderbilt (SUN); Alan Young
(Concurrent).
RFC 1327 has been widely adopted, and a review team was
formed. This comprised of: Urs Eppenberger (SWITCH)(Chair);
Claudio Allocchio (INFN); Harald Alvestrand (UNINETT); Dave
Crocker (Brandenburg); Ned Freed (Innosoft); Erik Huizer
(SURFnet); Steve Kille (Isode); Peter Sylvester (GC Tech)
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Harald Alvestrand also supplied the tables mapping DSN
status codes with X.400 codes. Ned Freed defined parts of the
File Transfer Body Part mapping.
Comment and input has also been received from: Bengt
Ackzell (Generic Systems); Samir Albadine (Transpac); Mark Boyes
(DEC); Larry Campbell (Boston Software Works); Jacqui Caren
(Cray); Allan Cargille (MCI); Kevin Carrosso (Innosoft); Charlie
Combs (OIW); Jim Craigie (Net-Tel); Eamon Doyle (Isocor); Efifion
Edem (SITA); Jyrki Heikkinen (ICL); Edward Hibbert (DCL); Jeroun
Houttin (Terena); Kevin Jordan (CDS); Paul Kingsnorth (DEC);
Carl-Uno Manros (Manros Consulting); Suzan Mendes (Telis); Robert
Miles (Softswitch); Roger Mizumorri (Enterprise Solutions Ltd);
Keith Moore (University of Tennessee); Ruth Moulton (Net-Tel)
Michel Musy (Bull); Kenji Nonaka (NTT): The OIW MHSIG; Tom
Oliphant (SWITCH); Julian Onions (NEXOR); Jacob Palme (KTH);
Olivier Paridaens (ULB); Mary la Roche (Citicorp); John Setsaas
(Maxware); Russell Sharpe (DCL); Patrick Soulier (CCETT);
Eftimios Tsigros (Universite Libre de Bruxelles); Sean Turner
(IECA); Mark Wahl (Isode); David Wilson (Isode); Bill Wohler
(Worldtalk); Alan Young (Isode); Alain Zahm (Telis).
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Chapter 2 - Service Elements
This chapter considers the services offered across a gateway
built according to this specification. It gives a view of the
functionality provided by such a gateway for communication with
users in the opposite domain. This chapter considers service
mappings in the context of SINGLE transfers only, and not
repeated mappings through multiple gateways.
2.1. The Notion of Service Across a Gateway
RFC 822 and X.400 provide a number of services to the end user.
This chapter describes the extent to which each service can be
supported across an X.400 <-> RFC 822 gateway. The cases
considered are single transfers across such a gateway, although
the problems of multiple crossings are noted where appropriate.
2.1.1. Origination of Messages
When a user originates a message, a number of services are
available. Some of these imply actions (e.g., delivery to a
recipient), and some are insertion of known data (e.g.,
specification of a subject field). This chapter describes, for
each offered service, to what extent it is supported for a
recipient accessed through a gateway. There are three levels of
support:
Supported
The corresponding protocol elements map well, and so the
service can be fully provided.
Not Supported
The service cannot be provided, as there is a complete
mismatch.
Partial Support
The service can be partially fulfilled.
In the first two cases, the service is simply marked as
"Supported" or "Not Supported". Some explanation may be given if
there are additional implications, or the (non) support is not
intuitive. For partial support, the level of partial support is
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summarised. Where partial support is good, this will be
described by a phrase such as "Supported by use of.....". A
common case of this is where the service is mapped onto a non-
standard service on the other side of the gateway, and this would
have lead to support if it had been a standard service. In many
cases, this is equivalent to support. For partial support, an
indication of the mechanism is given, in order to give a feel for
the level of support provided. Note that this is not a
replacement for Chapter 5, where the mapping is fully specified.
If a service is described as supported, this implies:
- Semantic correspondence.
- No (significant) loss of information.
- Any actions required by the service element.
An example of a service gaining full support: If an RFC 822
originator specifies a Subject: field, this is considered to be
supported, as an X.400 recipient will get a subject indication.
In many cases, the required action will simply be to make the
information available to the end user. In other cases, actions
may imply generating a delivery report.
All RFC 822 services are supported or partially supported
for origination. The implications of non-supported X.400
services is described under X.400.
2.1.2. Reception of Messages
For reception, the list of service elements required to support
this mapping is specified. This is really an indication of what
a recipient might expect to see in a message which has been
remotely originated.
2.2. RFC 822
RFC 822 does not explicitly define service elements, as distinct
from protocol elements. However, all of the RFC 822 header
fields, with the exception of trace, can be regarded as
corresponding to implicit RFC 822 service elements.
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2.2.1. Origination in RFC 822
A mechanism of mapping, used in several cases, is to map the RFC
822 header into a heading extension in the IPM (InterPersonal
Message). This can be regarded as partial support, as it makes
the information available to any X.400 implementations which are
interested in these services. Communities which require
significant RFC 822 interworking are recommended to require that
their X.400 User Agents are able to display these heading
extensions. Support for the various service elements (headers)
is now listed.
Date:
Supported.
From:
Supported. For messages where there is also a sender field,
the mapping is to "Authorising Users Indication", which has
subtly different semantics to the general RFC 822 usage of
From:.
Sender:
Supported.
Reply-To:
Supported.
To: Supported.
Cc: Supported.
Bcc: Supported.
Message-Id:
Supported.
In-Reply-To:
Supported, for a single reference. Where multiple
references are given, partial support is given by mapping to
"Cross Referencing Indication". This gives similar
semantics.
References:
Supported.
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Keywords:
Supported by use of a heading extension.
Subject:
Supported.
Comments:
Supported by use of a heading extension.
Encrypted:
Supported by use of a heading extension.
Content-Language:
Supported.
Resent-*
Supported by use of a heading extension. Note that
addresses in these fields are mapped onto text, and so are
not accessible to the X.400 user as addresses. In
principle, fuller support would be possible by mapping onto
a forwarded IP Message, but this is not suggested.
Other Fields
In particular X-* fields, and "illegal" fields in common
usage (e.g., "Fruit-of-the-day:") are supported by use of
heading extensions.
MIME introduces a number of headings. Support is defined in RFC
1494bis.
2.2.2. Reception by RFC 822
This considers reception by an RFC 822 User Agent of a message
originated in an X.400 system and transferred across a gateway.
The following standard services (headers) may be present in such
a message:
Date:
From:
Sender:
Reply-To:
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To:
Cc:
Bcc:
Message-Id:
In-Reply-To:
References:
Subject:
Content-Type: (See RFC 1494bis)
Content-Transfer-Encoding: (See RFC 1494bis)
MIME-Version: (See RFC 1494bis)
The following services (headers) may be present in the header of
a message. These are defined in more detail in Chapter 5 (5.3.4,
5.3.6, 5.3.7):
Autoforwarded:
Autosubmitted:
X400-Content-Identifier:
Content-Language:
Conversion:
Conversion-With-Loss:
Delivery-Date:
Discarded-X400-IPMS-Extensions:
Discarded-X400-MTS-Extensions:
DL-Expansion-History:
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Deferred-Delivery:
Expires:
Importance:
Incomplete-Copy:
Latest-Delivery-Time:
Message-Type:
Original-Encoded-Information-Types:
Originator-Return-Address:
Priority:
Reply-By:
Sensitivity:
Supersedes:
X400-Content-Type:
X400-MTS-Identifier:
X400-Originator:
X400-Received:
X400-Recipients:
2.3. X.400
2.3.1. Origination in X.400
When mapping services from X.400 to RFC 822 which are not
supported by RFC 822, new RFC 822 headers are defined, and
registered by publication in this standard. It is intended that
co-operating RFC 822 systems may also use them. Where these new
fields are used, and no system action is implied, the service can
be regarded as being partially supported. Chapter 5 describes
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how to map X.400 services onto these new headers. Other elements
are provided, in part, by the gateway as they cannot be provided
by RFC 822.
Some service elements are marked N/A (not applicable).
There are five cases, which are marked with different comments:
N/A (local)
These elements are only applicable to User Agent / Message
Transfer Agent interaction and so they cannot apply to RFC
822 recipients.
N/A (PDAU)
These service elements are only applicable where the
recipient is reached by use of a Physical Delivery Access
Unit (PDAU), and so do not need to be mapped by the gateway.
N/A (reception)
These services are only applicable for reception.
N/A (prior)
If requested, this service shall be performed prior to the
gateway.
N/A (MS)
These services are only applicable to Message Store (i.e., a
local service).
Finally, some service elements are not supported. In
particular, the new security services are not mapped onto RFC
822. Unless otherwise indicated, the behaviour of service
elements marked as not supported will depend on the criticality
marking supplied by the user. If the element is marked as
critical for transfer or delivery, a non-delivery notification
will be generated. Otherwise, the service request will be
ignored.
2.3.1.1. Basic Interpersonal Messaging Service
These are the mandatory IPM services as listed in Section 19.8 of
X.400 / ISO/IEC 10021-1, listed here in the order given. Section
19.8 has cross references to short definitions of each service.
Access management
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N/A (local).
Content Type Indication
Supported by a new RFC 822 header (X400-Content-Type:).
Converted Indication
Supported by a new RFC 822 header (X400-Received:).
Delivery Time Stamp Indication
N/A (reception).
IP Message Identification
Supported.
Message Identification
Supported, by use of a new RFC 822 header
(X400-MTS-Identifier). This new header is required, as
X.400 has two message-ids whereas RFC 822 has only one (see
IP Message Identification
Non-delivery Notification
Not supported in all cases. Supported where the recipient
system supports NOTARY DSNs. In general all RFC 822 systems
will return error reports by use of IP messages. In other
service elements, this pragmatic result can be treated as
effective support of this service element.
Original Encoded Information Types Indication
Supported as a new RFC 822 header
(Original-Encoded-Information-Types:).
Submission Time Stamp Indication
Supported.
Typed Body
Support is defined in RFC 1494bis.
User Capabilities Registration
N/A (local).
2.3.1.2. IPM Service Optional User Facilities
This section describes support for the optional (user selectable)
IPM services as listed in Section 19.9 of X.400 / ISO/IEC 10021-
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1, listed here in the order given. Section 19.9 has cross
references to short definitions of each service.
Additional Physical Rendition
N/A (PDAU).
Alternate Recipient Allowed
Not supported. There is no RFC 822 service equivalent to
prohibition of alternate recipient assignment (e.g., an RFC
822 system may freely send an undeliverable message to a
local postmaster). A MIXER gateway has two conformant
options. The first is not to gateway a message requesting
prohibition of alternate recipient, as this control cannot
be guaranteed. This option supports the service, but may
cause unacceptable level of message rejections. The second
is to gateway the message on the basis that there is no
alternate recipient service in RFC 822. RFC 1327 allowed
only the second option. If the first option is shown to be
operationally effective, it may be the only option in future
versions of MIXER.
Authorising User's Indication
Supported.
Auto-forwarded Indication
Supported as new RFC 822 header (Auto-Forwarded:).
Basic Physical Rendition
N/A (PDAU).
Blind Copy Recipient Indication
Supported.
Body Part Encryption Indication
Supported by use of a new RFC 822 header
(Original-Encoded-Information-Types:), although in most
cases it will not be possible to map the body part in
question.
Content Confidentiality
Not supported.
Content Integrity
Not supported.
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Conversion Prohibition
Supported. Operation defined in RFC 1494bis.
Conversion Prohibition in Case of Loss of Information
Supported. Operation defined in RFC 1494bis.
Counter Collection
N/A (PDAU).
Counter Collection with Advice
N/A (PDAU).
Cross Referencing Indication
Supported.
Deferred Delivery
N/A (prior). This service shall always be provided by the
MTS prior to the gateway. A new RFC 822 header
(Deferred-Delivery:) is provided to transfer information on
this service to the recipient.
Deferred Delivery Cancellation
N/A (local).
Delivery Notification
Supported. This is performed at the gateway, but may be
performed at the end system if the end system supports
NOTARY. Thus, a notification is sent by the gateway to the
originator.
Delivery via Bureaufax Service
N/A (PDAU).
Designation of Recipient by Directory Name
N/A (local).
Disclosure of Other Recipients
Supported by use of a new RFC 822 header (X400-Recipients:).
This is descriptive information for the RFC 822 recipient,
and is not reverse mappable.
DL Expansion History Indication
Supported by use of a new RFC 822 header
(DL-Expansion-History:).
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DL Expansion Prohibited
Distribution List means MTS supported distribution list, in
the manner of X.400. This service does not exist in the RFC
822 world, although RFC 822 supports distribution list
functionality. There is no SMTP leve control to prohibit
distribution list expansion. A MIXER gateway has two
conformant options. The first is not to gateway a message
requesting DL expansion prohibition, as this control cannot
be guaranteed. This option supports the service, but may
cause unacceptable level of message rejections. The second
is to gateway the message on the basis that there is no
distribution list service in RFC 822. RFC 1327 allowed only
the second option. If the first option is shown to be
operationally effective, it may be the only option in future
versions of MIXER.
Express Mail Service
N/A (PDAU).
Expiry Date Indication
Supported as new RFC 822 header (Expires:). In general, no
automatic action can be expected.
Explicit Conversion
N/A (prior).
Forwarded IP Message Indication
Supported.
Grade of Delivery Selection
Not Supported. There is no equivalent service in RFC 822.
Importance Indication
Supported as new RFC 822 header (Importance:).
Incomplete Copy Indication
Supported as new RFC 822 header (Incomplete-Copy:).
Language Indication
Supported as new RFC 822 header (Content-Language:).
Latest Delivery Designation
Not supported. A new RFC 822 header (Latest-Delivery-Time:)
is provided, which may be used by the recipient for general
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information, but will not be acted on by the SMTP
infrastrucuture.
Message Flow Confidentiality
Not supported.
Message Origin Authentication
N/A (reception).
Message Security Labelling
Not supported.
Message Sequence Integrity
Not supported.
Multi-Destination Delivery
Supported.
Multi-part Body
Supported.
Non Receipt Notification Request
Not supported.
Non Repudiation of Delivery
Not supported.
Non Repudiation of Origin
N/A (reception).
Non Repudiation of Submission
N/A (local).
Obsoleting Indication
Supported as new RFC 822 header (Supersedes:).
Ordinary Mail
N/A (PDAU).
Originator Indication
Supported.
Originator Requested Alternate Recipient
Not supported, but is placed as comment next to address
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(X400-Recipients:).
Physical Delivery Notification by MHS
N/A (PDAU).
Physical Delivery Notification by PDS
N/A (PDAU).
Physical Forwarding Allowed
Supported by use of a comment in a new RFC 822 header
(X400-Recipients:), associated with the recipient in
question.
Physical Forwarding Prohibited
Supported by use of a comment in a new RFC 822 header
(X400-Recipients:), associated with the recipient in
question.
Prevention of Non-delivery notification
Supported where SMTP and NOTARY are available. In other
cases formally supported, as delivery notifications cannot
be generated by RFC 822. In practice, errors will be
returned as IP Messages, and so this service may appear not
to be supported (see Non-delivery Notification).
Primary and Copy Recipients Indication
Supported
Probe
Supported at the gateway (i.e., the gateway services the
probe).
Probe Origin Authentication
N/A (reception).
Proof of Delivery
Not supported.
Proof of Submission
N/A (local).
Receipt Notification Request Indication
Not supported.
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Redirection Disallowed by Originator
Redirection means MTS supported redirection, in the manner
of X.400. This service does not exist in the RFC 822 world.
RFC 822 redirection (e.g., aliasing) is regarded as an
informal redirection mechanism, beyond the scope of this
control. Messages will be sent to RFC 822, irrespective of
whether this service is requested. In practice, control of
this service is not supported.
Registered Mail
N/A (PDAU).
Registered Mail to Addressee in Person
N/A (PDAU).
Reply Request Indication
Supported as comment next to address.
Replying IP Message Indication
Supported.
Report Origin Authentication
N/A (reception).
Request for Forwarding Address
N/A (PDAU).
Requested Delivery Method
N/A (local). The service request is dealt with at
submission time. Any such request is made available through
the gateway by use of a comment associated with the
recipient in question.
Return of Content
Supported where SMTP and NOTARY are used. In principle for
other situations, this is N/A, as non-delivery notifications
are not supported. In practice, most RFC 822 systems will
return part or all of the content along with the IP Message
indicating an error (see Non-delivery Notification).
Sensitivity Indication
Supported as new RFC 822 header (Sensitivity:).
Special Delivery
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N/A (PDAU).
Stored Message Deletion
N/A (MS).
Stored Message Fetching
N/A (MS).
Stored Message Listing
N/A (MS).
Stored Message Summary
N/A (MS).
Subject Indication
Supported.
Undeliverable Mail with Return of Physical Message
N/A (PDAU).
Use of Distribution List
In principle this applies only to X.400 supported
distribution lists (see DL Expansion Prohibited).
Theoretically, this service is N/A (prior). In practice,
because of informal RFC 822 lists, this service can be
regarded as supported.
Auto-Submitted Indication
Supported
2.3.2. Reception by X.400
2.3.2.1. Standard Mandatory Services
The following standard IPM mandatory user facilities are
required for reception of RFC 822 originated mail by an X.400 UA.
Content Type Indication
Delivery Time Stamp Indication
IP Message Identification
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Message Identification
Non-delivery Notification
Original Encoded Information Types Indication
Submission Time Stamp Indication
Typed Body
2.3.2.2. Standard Optional Services
The following standard IPM optional user facilities are required
for reception of RFC 822 originated mail by an X.400 UA.
Authorising User's Indication
Blind Copy Recipient Indication
Cross Referencing Indication
Originator Indication
Primary and Copy Recipients Indication
Replying IP Message Indication
Subject Indication
2.3.2.3. New Services
A new X.400 service "RFC 822 Header Field" is defined using the
extension facilities. This allows for any RFC 822 header field
to be represented. It may be present in RFC 822 originated
messages which are received by an X.400 UA.
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Chapter 3 Basic Mappings
3.1. Notation
The X.400 protocols are encoded in a structured manner according
to ASN.1, whereas RFC 822 is text encoded. To define a detailed
mapping, it is necessary to refer to detailed protocol elements
in each format. A notation to achieve this is described in this
section.
3.1.1. RFC 822
Structured text is defined according to the Extended Backus Naur
Form (EBNF) defined in Section 2 of RFC 822 [16]. In the EBNF
definitions used in this specification, the syntax rules given in
Appendix D of RFC 822 are assumed. When these EBNF tokens are
referred to outside an EBNF definition, they are identified by
the string "822." appended to the beginning of the string (e.g.,
822.addr-spec). Additional syntax rules, to be used throughout
this specification, are defined in this chapter.
The EBNF is used in two ways.
1. To describe components of RFC 822 messages (or of SMTP
components). When these new EBNF tokens are referred to
outside an EBNF definition, they are identified by the
string "EBNF." appended to the beginning of the string
(e.g., EBNF.importance).
2. To describe the structure of IA5 or ASCII information not in
an RFC 822 message.
For all new EBNF, tokens will either be self delimiting, or be
delimited by self delimiting tokens. Comments and LWSP are not
used as delimiters, except for the following cases, where LWSP
may be inserted according to RFC 822 rules.
- Around the ":" in all headers
- EBNF.labelled-integer
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- EBNF.object-identifier
- EBNF.encoded-info
RFC 822 folding rules are applied to all headers. Comments are
never used in these new headers.
This notation is used in a modified form to refer to NOTARY
EBNF [28]. For this EBNF, the keyword EBNF it replaces with DSN,
for example DSN.final-recipient-field fields.
3.1.2. ASN.1
An element is referred to with the following syntax, defined in
EBNF:
element = service "." definition *( "." definition )
service = "IPMS" / "MTS" / "MTA"
definition = identifier / context
identifier = ALPHA *< ALPHA or DIGIT or "-" >
context = "[" 1*DIGIT "]"
The EBNF.service keys are shorthand for the following service
specifications:
IPMS IPMSInformationObjects defined in Annex E of X.420 / ISO
10021-7.
MTS MTSAbstractService defined in Section 9 of X.411 / ISO
10021-4.
MTA MTAAbstractService defined in Section 13 of X.411 / ISO
10021-4.
FTBP File Transfer Body Part, as defined in [27].
The first EBNF.identifier identifies a type or value key in the
context of the defined service specification. Subsequent
EBNF.identifiers identify a value label or type in the context of
the first identifier (SET or SEQUENCE). EBNF.context indicates a
context tag, and is used where there is no label or type to
uniquely identify a component. The special EBNF.identifier
keyword "value" is used to denote an element of a sequence.
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For example, IPMS.Heading.subject defines the subject element of
the IPMS heading. The same syntax is also used to refer to
element values. For example,
MTS.EncodedInformationTypes.[0].g3Fax refers to a value of
MTS.EncodedInformationTypes.[0] .
3.2. ASCII and IA5
A gateway will interpret all IA5 as ASCII. Thus, mapping between
these forms is conceptual.
3.3. Standard Types
There is a need to convert between ASCII text and some of the
types defined in ASN.1 [14]. For each case, an EBNF syntax
definition is given, for use in all of this specification, which
leads to a mapping between ASN.1, and an EBNF construct. All
EBNF syntax definitions of ASN.1 types are in lower case, whereas
ASN.1 types are referred to with the first letter in upper case.
Except as noted, all mappings are symmetrical.
3.3.1. Boolean
Boolean is encoded as:
boolean = "TRUE" / "FALSE"
3.3.2. NumericString
NumericString is encoded as:
numericstring = *(DIGIT / " ")
3.3.3. PrintableString
PrintableString is a restricted IA5String defined as:
printablestring = *( ps-char )
ps-restricted-char = 1DIGIT / 1ALPHA / " " / "'" / "+"
/ "," / "-" / "." / "/" / ":" / "=" / "?"
ps-delim = "(" / ")"
ps-char = ps-delim / ps-restricted-char
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This can be used to represent real printable strings in EBNF.
3.3.4. T.61String
In cases where T.61 strings are only used for conveying human
interpreted information, the aim of a mapping is to render the
characters appropriately in the remote character set, rather than
to maximise reversibility. For these cases, there are two
options, both of which are conformant to this specification:
1. The mappings to IA5 defined in ITU-T Recommendation X.408
(1988) may be used [13]. These will then be encoded in
ASCII. This is the approach mandated in RFC 1327.
2. This mapping may be used if the characters are not contained
within ASCII repertoire, but are all in an IANA-registered
character set. Use the encoding defined in RFC 1522 [9] to
generate appropriate encoded-words. If this mapping is
used, the character set ISO-8859-1 shall be used if all of
the characters needed are available in this repertoire. In
other cases, the character set TELETEX shall be used. The
details of this character set is defined in the Appendix C
of RFC1494bis.
There is also a need to represent Teletex Strings in ASCII,
for some aspects of OR Address. For these, the following
encoding is used:
teletex-string = *( ps-char / t61-encoded )
t61-encoded = "{" 1* t61-encoded-char "}"
t61-encoded-char = 3DIGIT
Characters in EBNF.ps-char are mapped simply. Other octets,
including control characters, are mapped using a quoting
mechanism similar to the printable string mechanism. Each octet
is represented as 3 decimal digits. For example, the Yen
character (hex A5) is represented as {165}. As the three
character string, a, yen character, b, would be represented as
either "a{165}b".
The use of escape sequences follows that set down for ASN1.
in ISO 8825-1, with the additional specifiction that the default
G1 page is ISO Latin 1. The page settings may be changed by
escape sequences. Changes of the settings hold within a pair of
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curly brackets ({}), and the settings revert to the default after
the right bracket (}) (i.e., they do not carry forward to
subsequent T.61 encoding).
There are a number of places where a string may have a Teletex
and/or Printable String representation. The following EBNF is
used to represent this.
teletex-and-or-ps = [ printablestring ] [ "*" teletex-string ]
The natural mapping is restricted to EBNF.ps-char, in order to
make the full BNF easier to parse. An example is:
"yen*{165}"
3.3.5. UTCTime
Both UTCTime and the RFC 822 822.date-time syntax contain: Year,
Month, Day of Month, hour, minute, second (optional), and
Timezone (technically a time differential in UTCTime).
822.date-time also contains an optional day of the week, but this
is redundant. With the exception of Year, a symmetrical mapping
can be made between these constructs.
Note:
In practice, a gateway will need to parse various illegal
variants on 822.date-time. In cases where 822.date-time
cannot be parsed, it is recommended that the derived UTCTime
is set to the value at the time of translation. Such errors
may be noted in an RFC 822 comment, to aid detection and
correction.
When mapping to X.400, the UTCTime format which specifies the
timezone offset shall be used.
When mapping to RFC 822, the 822.date-time format shall include a
numeric timezone offset (e.g., -0500).
When mapping time values, the timezone shall be preserved as
specified. The date shall not be normalised to any other
timezone.
RFC 822, as modified by RFC 1123, requires use of a four digit
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year. Note that the original RFC 822 uses a two digit date,
which is no longer legal. UTCTime uses a two digit date. To map
a year from RFC 822 to X.400, simply use the last two digits.
To map a year from X.400 to RFC 822, assume that the two digit
year refers to a year in the 10 year epoch 1980-2079.
3.3.6. Integer
A basic ASN.1 Integer will be mapped onto EBNF.numericstring. In
many cases ASN.1 will enumerate Integer values or use ENUMERATED.
An EBNF encoding labelled-integer is provided. When mapping from
EBNF to ASN.1, only the integer value is mapped, and the
associated text is discarded. When mapping from ASN.1 to EBNF, a
text label may be added. It is recommended that this is done
wherever possible and that clear text labels are chosen.
A second encoding labelled-integer-2 is provided. This is
used in DSNs, where the parsing rules will treat the text as a
comment. This definition was not present in RFC 1327.
labelled-integer ::= [ key-string ] "(" numericstring ")"
labelled-integer-2 ::= [ numericstring ] "(" key-string ")"
key-string = *key-char
key-char = <a-z, A-Z, 0-9, and "-">
3.3.7. Object Identifier
Object identifiers are represented in a form similar to that
given in ASN.1. The order is the same as for ASN.1 (big-endian).
The numbers are mandatory, and used when mapping from the ASCII
to ASN.1. The key-strings are optional. It is recommended that
as many strings as possible are generated when mapping from ASN.1
to ASCII, to facilitate user recognition.
object-identifier ::= oid-comp object-identifier
| oid-comp
oid-comp ::= [ key-string ] "(" numericstring ")"
An example representation of an object identifier is:
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joint-iso-ccitt(2) mhs (6) ipms (1) ep (11) ia5-text (0)
or
(2) (6) (1)(11)(0)
Because of the use of brackets and the conflict with the RFC 822
comment convention, MIXER is defines so that the EBNFobject-
identifier definition is not used in structured fields.
3.4. Encoding ASCII in Printable String
Some information in RFC 822 is represented in ASCII, and needs to
be mapped into X.400 elements encoded as printable string. For
this reason, a mechanism to represent ASCII encoded as
PrintableString is needed.
A structured subset of EBNF.printablestring is now defined.
This shall be used to encode ASCII in the PrintableString
character set.
ps-encoded = *( ps-restricted-char / ps-encoded-char )
ps-encoded-char = "(a)" ; (@)
/ "(p)" ; (%)
/ "(b)" ; (!)
/ "(q)" ; (")
/ "(u)" ; (_)
/ "(l)" ; "("
/ "(r)" ; ")"
/ "(" 3DIGIT ")"
The 822.3DIGIT in EBNF.ps-encoded-char shall have range 0-127,
and is interpreted in decimal as the corresponding ASCII
character. Special encodings are given for: at sign (@), percent
(%), exclamation mark/bang (!), double quote ("), underscore (_),
left bracket ((), and right bracket ()). These characters, with
the exception of round brackets, are not included in
PrintableString, but are common in RFC 822 addresses. The
abbreviations will ease specification of RFC 822 addresses from
an X.400 system. These special encodings shall be interpreted in
a case insensitive manner, but always generated in lower case.
A reversible mapping between PrintableString and ASCII can
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now be defined. The reversibility means that some values of
printable string (containing round braces) cannot be generated
from ASCII. Therefore, this mapping shall only be used in cases
where the printable strings have been derived from ASCII (and
will therefore have a restricted domain). For example, in this
specification, it is only applied to a Domain Defined Attribute
which will have been generated by use of this specification and a
value such as "(" would not be possible.
To encode ASCII as PrintableString, the EBNF.ps-encoded
syntax is used, with all EBNF.ps-restricted-char mapped directly.
All other 822.CHAR are encoded as EBNF.ps-encoded-char.
To encode PrintableString as ASCII, parse PrintableString as
EBNF.ps-encoded, and then reverse the previous mapping. If the
PrintableString cannot be parsed, then the mapping is being
applied in to an inappropriate value, and an error shall be given
to the procedure doing the mapping. In some cases, it may be
preferable to pass the printable string through unaltered.
Some examples are now given. Note the arrows which indicate
asymmetrical mappings:
PrintableString ASCII
'a demo.' <-> 'a demo.'
foo(a)bar <-> foo@bar
(q)(u)(p)(q) <-> "_%"
(a) <-> @
(A) -> @
(l)a(r) <-> (a)
(126) <-> ~
( -> (
(l) <-> (
3.5. RFC 1522
RFC 1522 defines a mechanism for encoding other character set
information into elements of RFC 822 Headers. A gateway may
ignore this encoding and treat the elements as ASCII.
A preferred approach is for the gateway to interpret the RFC
1522 encoding. This will not always be straightforward, because:
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1. RFC 1522 permits an openly extensible character set choice,
which may be broader than T.61.
2. It is not always possible to map all characters into the
equivalent X.400 field.
RFC 1522 is only applied to fields which are "for information
only". A gateway which interprets header elements according to
RFC 1522 may apply reasonable heuristics to minimise information
loss.
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Chapter 4 - Addressing and Message IDs
Addressing is the most complex aspect of X.400 <-> RFC 822
gateway and is therefore given a separate chapter. This chapter
also discusses message identifiers, as they are closely linked to
addresses. This chapter, as a side effect, also defines a
textual representation of an X.400 OR Address. This
specification has much similarity to the X.400(92) representation
of addresses. This was because early versions of this
specification were a major input to this work. This
specification retains compatibility with earlier versions. The
X.400 specification of address representation can be parsed but
is not generated.
Initially we consider an address in the (human) mail user
sense of "what is typed at the mailsystem to reference a mail
user". A basic RFC 822 address is defined by the EBNF
EBNF.822-address:
822-address = [ route ] addr-spec
These definitions are taken from RFC 822. In SMTP (or another
822-MTS protocol), the originator and each recipient are
considered to be defined by such a construct. In an RFC 822
header, the EBNF.822-address is encapsulated in the 822-address
syntax rule, and there may also be associated comments. None of
this extra information has any semantics, other than to the end
user.
The basic X.400 OR Address, used by the MTS for routing, is
defined by MTS.ORAddress. In IPMS, the MTS.ORAddress is
encapsulated within IPMS.ORDescriptor.
The RFC 822 822.address is mapped with IPMS.ORDescriptor,
and that RFC 822 EBNF.822-address is mapped with MTS.ORAddress.
Section 4.1 defines a textual representation of an OR
Address, which is used throughout the rest of this specification.
This text representation is designed to represent an X.400
address in the LHS (left hand side) or local part of an RFC 822
address, and so this representation gives a mechanism to
represent X.400 addresses within RFC 822 addresses.
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Section 4.2 describes global equivalence mapping between
parts of the X.400 and RFC 822 name spaces, and defines the
concept of a MIXER Conformant Global Address Mapping (MCGAM).
Gateways conforming to this specification shall support MCGAMs.
Section 4.3 is the core part of this chapter, and defines
the mapping mechanism.
4.1. A textual representation of MTS.ORAddress
MTS.ORAddress is structured as an ordered set of attributes
(type/value pairs). It is clearly necessary to be able to encode
this in ASCII for gatewaying purposes. All components shall be
encoded, in order to guarantee return of error messages, and to
optimise third party replies.
4.1.1. Basic OR Address Representation
An OR Address has a number of structured and unstructured
attributes. For each unstructured attribute, a key and an
encoding is specified. For structured attributes, the X.400
attribute is mapped onto one or more attribute value pairs. For
domain defined attributes, each element of the sequence will be
mapped onto a triple (key and two values), with each value having
the same encoding. The attributes are as follows, with 1984
attributes given in the first part of the attribute key table.
For each attribute, a reference is given, consisting of the
relevant sections in X.402 / ISO 10021-2, and the extension
identifier for 88 only attributes. The attribute key table
follows:
Attribute (Component) Key Enc Ref Id
84/88 Attributes
MTS.CountryName C P 18.3.3
MTS.AdministrationDomainName ADMD P 18.3.1
MTS.PrivateDomainName PRMD P 18.3.21
MTS.NetworkAddress X121 N 18.3.7
MTS.TerminalIdentifier T-ID P 18.3.23
MTS.OrganizationName O P/T 18.3.9
MTS.OrganizationalUnitNames.value OU P/T 18.3.10
MTS.NumericUserIdentifier UA-ID N 18.3.8
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MTS.PersonalName PN P/T 18.3.12
MTS.PersonalName.surname S P/T 18.3.12
MTS.PersonalName.given-name G P/T 18.3.12
MTS.PersonalName.initials I P/T 18.3.12
MTS.PersonalName
.generation-qualifier GQ P/T 18.3.12
MTS.DomainDefinedAttribute.value DD P/T 18.1
88 Attributes
MTS.CommonName CN P/T 18.3.2 1
MTS.TeletexCommonName CN P/T 18.3.2 2
MTS.TeletexOrganizationName O P/T 18.3.9 3
MTS.TeletexPersonalName PN P/T 18.3.12 4
MTS.TeletexPersonalName.surname S P/T 18.3.12 4
MTS.TeletexPersonalName.given-name G P/T 18.3.12 4
MTS.TeletexPersonalName.initials I P/T 18.3.12 4
MTS.TeletexPersonalName
.generation-qualifier GQ P/T 18.3.12 4
MTS.TeletexOrganizationalUnitNames
.value OU P/T 18.3.10 5
MTS.TeletexDomainDefinedAttribute
.value DD P/T 18.1 6
MTS.PDSName PD-SERVICE P 18.3.11 7
MTS.PhysicalDeliveryCountryName PD-C P 18.3.13 8
MTS.PostalCode PD-CODE P 18.3.19 9
MTS.PhysicalDeliveryOfficeName PD-OFFICE P/T 18.3.14 10
MTS.PhysicalDeliveryOfficeNumber PD-OFFICE-NUM P/T 18.3.15 11
MTS.ExtensionORAddressComponents PD-EXT-ADDRESS P/T 18.3.4 12
MTS.PhysicalDeliveryPersonName PD-PN P/T 18.3.17 13
MTS.PhysicalDeliveryOrganizationName PD-O P/T 18.3.16 14
MTS.ExtensionPhysicalDelivery
AddressComponents PD-EXT-DELIVERY P/T 18.3.5 15
MTS.UnformattedPostalAddress PD-ADDRESS UPA 18.3.25 16
MTS.StreetAddress PD-STREET P/T 18.3.22 17
MTS.PostOfficeBoxAddress PD-BOX P/T 18.3.18 18
MTS.PosteRestanteAddress PD-RESTANTE P/T 18.3.20 19
MTS.UniquePostalName PD-UNIQUE P/T 18.3.26 20
MTS.LocalPostalAttributes PD-LOCAL P/T 18.3.6 21
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MTS.ExtendedNetworkAddress
.e163-4-address.number NET-NUM N 18.3.7 22
MTS.ExtendedNetworkAddress
.e163-4-address.sub-address NET-SUB N 18.3.7 22
MTS.ExtendedNetworkAddress
.psap-address NET-PSAP X 18.3.7 22
MTS.TerminalType T-TY I 18.3.24 23
The following keys identify different EBNF encodings, which are
associated with the ASCII representation of MTS.ORAddress.
Key Encoding
P printablestring
N numericstring
T teletex-string
P/T teletex-and-or-ps
UPA upa-string
I labelled-integer
X presentation-address
The EBNF for presentation-address is taken from the specification
RFC 1278 "A String Encoding of Presentation Address" [23].
In most cases, the EBNF encoding maps directly to the ASN.1
encoding of the attribute. There are a few exceptions. In cases
where an attribute can be encoded as either a PrintableString or
NumericString (Country, ADMD, PRMD), either form is mapped into
the EBNF. When generating ASN.1, the NumericString encoding
shall be used if the string contains digits and only digits.
There are a number of cases where the P/T (teletex-and-or-ps)
representation is used. Where the key maps to a single
attribute, this choice is reflected in the encoding of the
attribute (attributes 10-21). For example:
/CN=yen*{165}/
For most of the 1984 attributes and common name, there is a
printablestring and a teletex variant. This pair of attributes
is mapped onto the single component here. This will give a clean
mapping for the common cases where only one form of the name is
used. If there is teletex attribute or teletex component only,
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and it contains only characters in the printable string character
set, it shall be represented in the EBNF as if it had been
encoded as printable string. A single printable string
representation shall also be done when both forms are present and
they have the same printable string representation.
The Unformatted Postal Address has a slightly more complex
mapping onto a variant of (teletex-and-or-ps), defined as:
upa-string = [ printable-upa ] [ "*" teletex-string ]
printable-upa = printablestring *( "|" printablestring )
The optional teletex part is straightforward. There is an
(optional) sequence of printable strings which are mapped in
order. For example:
/PD-ADDRESS=The Dome|The Square|Richmond|England/
X.400 (1992) has introduced a string representation of OR
Addresses (see F.401, Annex B). This has specified a number of
string keywords for attributes. As earlier versions of this
specification were an input to this work, many of the keywords
are the same. To increase compatibility, the following
alternative values shall be recognised when mapping from RFC 822
to X.400. These shall not be generated when mapping from X.400
to RFC 822. The following keyword alternative table and the
subsequent paragraph lists alternative keywords.
Keyword Alternative
ADMD A
PRMD P
GQ Q
X121 X.121
UA-ID N-ID
PD-OFFICE-NUM PD-OFFICE NUMBER
PD-OFFICE-NUM PD-OFN
PD-EXT-ADDRESS PD-EA
PD-EXT-DELIVERY PD-ED
PD-OFFICE PD-OF
PD-STREET PD-S
PD-UNIQUE PD-U
PD-LOCAL PD-L
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PD-RESTANTE PD-R
PD-BOX PD-B
PD-CODE PD-PC
PD-SERVICE PD-SN
DD DDA
NET-NUM E.164
NET-PSAP PSAP
PD-ADDRESS PD-A
When mapping from RFC 822 to X.400, the keywords defined in this
paragraph shall be recognized. The ordered keywords: OU1, OU2,
OU3, and OU4, shall be recognised. If these are present, no
keyword OU shall be present. These will be treated as ordered
values of OU. PD-A1, PD-A2, PD-A3, PD-A4, PD-A5, PD-A6 shall be
treated as ordered lines. If present, these will be assembled
with separating line feeds to form a single physical address. In
this case PD-ADDRESS (or PD-A) shall not be present. Similarly,
there are ordered keywords for domain defined attributes: DD1,
DD2, DD3, DD4,
If ISDN is present, it may be interpreted as an E.163/164
address, using local heuristics to parse the string. X.400
defines the key, but does not give an interpretation of the
value.
For T-TY (Terminal Type), the X.400 recommended values are
preferred, but other values are allowed. These values are: tlx
(3); ttx (4); g3fax (5); g4fax (6); ia5 (7); and vtx (8).
4.1.2. Encoding of Personal Name
Handling of Personal Name and Teletex Personal Name is a common
requirement. Therefore MIXER defines an alternative to the
EBNF.standard-type syntax, which utilises the "human" conventions
for encoding these components. A syntax is defined, which is
designed to provide a clean encoding for the common cases of OR
Address specification where:
1. There is no generational qualifier
2. Initials, if present, contain only letters
3. Given Name, if present, does not contain full stop ("."),
and is at least two characters long.
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4. Surname does not contain full stop in the first two
characters.
5 If Surname is the only component, it does not contain full
stop.
The following EBNF is defined:
encoded-pn = [ given "." ] *( initial "." ) surname
given = 2*<ps-char not including ".">
initial = ALPHA
surname = printablestring
This is used to map from any string containing only printable
string characters to an OR address personal name. To map from a
string to OR Address components, parse the string according to
the EBNF. The given name and surname are assigned directly. All
EBNF.initial tokens are concatenated without intervening full
stops to generate the initials component.
For an OR address which follows the above restrictions, a
string is derived in the natural manner. In this case, the
mapping will be reversible.
For example:
GivenName = "Marshall"
Surname = "Rose"
Maps with "Marshall.Rose"
Initials = "MT"
Surname = "Rose"
Maps with "M.T.Rose"
GivenName = "Marshall"
Initials = "MT"
Surname = "Rose"
Maps with "Marshall.M.T.Rose"
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Note that X.400 suggests that Initials is used to encode all
initials except the surname (X.402 section 18.3.12). Therefore,
the defined encoding is "natural" when either GivenName or
Initials, but not both, are present. The case where both are
present can be encoded.
4.1.3. Standard Encoding of MTS.ORAddress
Given this structure, we can specify an EBNF representation of an
OR Address. The output format of addresses is defined by
EBNF.std-or-address. The more flexible input format is defined
by EBNF.std-or-address-input. The input EBNF has been added
subsequent to RFC 1327, to reflect the formal incorporation of a
number of heuristics. The address element separator on input may
be "/", ";", or a mixture of these. The output format is used in
all examples.
std-or-address = 1*( "/" attribute "=" value ) "/"
attribute = standard-type
/ "RFC-822"
/ dd-key "." std-printablestring
std-or-address-input = [ sep pair ] sep pair *( sep pair )
sep [ pair sep ]
sep = "/" / ";"
pair = input-attribute "=" value
input-attribute = attribute
/ dd-key ":" std-printablestring
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standard-type = key-string
dd-key = key-string
value = std-printablestring
std-printablestring
= *( std-char / std-pair )
std-char = <"{", "}", "*", and any ps-char
except "/" and "=" >
std-pair = "$" ps-char
For address generation, the standard-type is any key defined in
the key table in Section 4.1, except PN, and DD. For address
parsing, other key values from Section 4.1 are also valid. The
EBNF leads to a set of attribute/value pairs. The value is
interpreted according to the EBNF encoding defined in the table.
If the standard-type is PN, the value is interpreted
according to EBNF.encoded-pn, and the components of
MTS.PersonalName and/or MTS.TeletexPersonalName derived
accordingly.
If dd-key is the recognised Domain Defined string (DD) or
one of the alternatives defined in Section 4.1, then the type and
value are interpreted according to the syntax implied from the
encoding, and aligned to either the teletex or printable string
form. Key and value shall have the same encoding.
If value is "RFC-822", then the (printable string) Domain
Defined Type of "RFC-822" is assumed. This is an optimised
encoding of the domain defined type defined by this
specification.
The matching of all keywords shall be done in a case-
independent manner.
EBNF.std-or-address uses the characters "/" and "=" as
delimiters. Domain Defined Attributes and any value may contain
these characters. A quoting mechanism, using the non-printable
string "$" is used to allow these characters to be represented.
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If an address of this syntax is parsed, and a country value
is present, but no ADMD, the string shall be interpreted as if an
ADMD value of single space had been specified.
4.2. Global Address Mapping
From a user perspective, the ideal mapping would be entirely
symmetrical and global, to enable addresses to be referred to
transparently in the remote system, with the choice of gateway
being left to the Message Transfer Service. There are two
fundamental reasons why this is not possible:
1. The syntaxes are sufficiently different to make this
impossible.
2 There is insufficient administrative co-operation between
the X.400 and RFC 822 name registration authorities for this
to work.
Another way to view this situation is to see that there is not a
full global equivalence between X.400 and RFC 822 addressing. To
meet user needs to the extent possible, this specification
provides for equivalence where there is sufficient co-operation.
To be useful, this equivalence shall be recognised and
interpreted in the same way by all gateways. Therefore, an
asymmetrical mapping is defined, which can be symmetrical where
there is appropriate administrative co-operation. Section 4.3
describes the asymetrical aspects. This section describes a
mechanism to enable the administrative co-ordination for
symmetrical mappings.
In order to achieve a symmetrical mapping there is a need to
define an administrative equivalence between parts of the OR
Address and Domain namespaces. Previous version of this
specification did this by definition of a global set of mappings.
MIXER defines the concept of a MIXER Conformant Global Address
Mapping (MCGAM). This acronym is defined so that it is very
clear what is being referenced.
The X.400 and Internet Mail address spaces are hierarchical.
It is possible to define an equivalence between two points in the
hierarchies, such that addresses below that point can be derived
in an algorithmic manner. An MCGAM is a mapping from a point in
one hierarchy to a point in the other hierarchy. An "MGGAM pair"
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is a pair of symmetrical mappings between two points. To define
an MCGAM, the following shall apply:
1. The authority defining the MCGAM shall have responsibility
for BOTH of the namespaces between which the MCGAM is
defined.
2. The authority defining the MCGAM is responsible to ensure
that addresses allocated below the two equivalence points
conform to the rules set out below.
3. The authority defining the MCGAM is responsible to ensure
that addresses which are generated according to the MCGAM
are routed correctly.
In general, MCGAMs will be independent. In some cases, a set of
MCGAMs may be related (e.g., where one MCGAM defines a mapping
for an organization and a second MCGAM defines an excpetion for a
subtree within the organization). In this case, the related set
of MCGAMs shall be treated as a single MCGAM for distribution
purposes.
The existence of an MCGAM does not imply routability and
access for all users.
The authority defining an MCGAM may simply use this mapping
locally. This will often be the case in a "local scenario"
gateway. Because of third party addressing, a MIXER gateway
will work best with the maximum number of MCGAMs. Therefore,
three mechanisms are defined to enable publication and exchange
of MCGAMs:
1. Distribution of text tables. This is described in Appendix
F of this specification.
2. Distribution by Domain Name Service. This is described in
RFC 1664bis [3].
3. Distribution by X.500 Directory Service. This is defined
in RFC 1838 [26].
The following sections define how the MCGAM namespace
equivalence is modelled. The Internet Domain Namespace defines a
simple hierarchy. For the purposes of this mapping, only parts
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of the namespace where domains conform to the EBNF domain-syntax
are allowed.
domain-syntax = alphanum [ *alphanumhyphen alphanum ]
alphanum = <ALPHA or DIGIT>
alphanumhyphen = <ALPHA or DIGIT or HYPHEN>
Although RFC 822 allows for a more general syntax, this
restricted syntax is used in MIXER as it is the one chosen by the
various domain service administrations. In practice, it reflects
all RFC 822 usage.
The following OR Address attributes are considered as a
hierarchy, and may be specified by the domain. They are (in
order of the hierarchy defined by MIXER):
Country, ADMD, PRMD, Organization, Organizational Units
There may be up to four ordered Organizational Units. This
hierarchy reflects most usage of X.400, although X.400 may be
used in other ways. In particular, it covers the Mnemonic OR
Address using a 1984 compatible encoding. This is seen as the
dominant form of OR Address. MCGAMs may only be used when this
hierarchy applies.
An equivalence mapping is defined between two nodes in the
respective hierarchies. For example:
=> "AC.UK" might be mapped with
PRMD="UK.AC", ADMD="GOLD 400", C="GB"
The mapping identifies that the management of these points in the
respective hierarchies is the same (or co-operate very closely).
The equivalence means that the namespaces below this equivalence
point map 1:1, except where the mapping is overridden by further
equivalence mappings lower down the hierarchy. This equivalence
may be achieved in three ways:
1. All of the nodes below this point are RFC 822, and the MIXER
mapping defines the X.400 addresses for these nodes.
2. All of the nodes below this point are X.400, and the MIXER
mapping defines the RFC 822 addresses for these nodes.
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3. There are X.400 and RFC 822 nodes below this point, and
addressing is managed in a manner which ensures the
equivalence. The rules to achieve this are defined by
MIXER.
Each of these ways gives a framework for MCGAM definition.
When an MCGAM is defined, a systematic mapping for the
inferior nodes in the two hierarchies follows. This is a 1:1
mapping between the nodes in the subtrees. For example, given
the MCGAM pair defined above:
the domain "R-D.Salford.AC.UK" algorithmically maps with
OU="R-D", O="Salford", PRMD="UK.AC", ADMD="GOLD 400", C="GB"
Note that when an equivalence is defined, that this can be re-
defined for lower points in the hierarchy. However, it is not
possible to declare contained subtrees to be un-mappable.
The equivalence mapping also provides a mechanism to deal
with missing elements in the X.400 hierarchy (most commonly the
PRMD, which is the only element that may be ommitted when
conforming to recent versions of X.400). A domain may be
associated with an omitted attribute in conjunction with several
present ones. When performing the algorithmic insertion of
components lower in the hierarchy, the omitted value shall be
skipped. For example:
If there is an MCGAM pair between domain HNE.EGM" and
"O=HNE", "ADMD=ECQ", "C=TC", and omitted PRMD
then
"ZI.HNE.EGM" is algorithmically mapped with
"OU=ZI", "O=HNE", "ADMD=ECQ", "C=TC"
Attributes may have null values, and this is treated separately
from omitted attributes (while it is not ideal
to make this distinction, it is useful in practice).
4.2.1. Directory and Nameserver Mappings
When a set of MCGAMs are supported by X.500 or DNS, there is the
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possibility that results will be indeterminate due to timeout.
Lookup shall be repeated until a value is determined, in order to
maintain consistent gateway operation.
Where the mapping relates to an envelope address, the
gateway shall non-deliver messages according to the associated
MTA's normal timeout policy. Where the mapping relates to
addresses in the message header, there shall be a timeout in the
range of 1-4 hours or shorter if this is required to maintain
quality of service constraints. If a mapping cannot be done in
this time, address encapsulation shall be used.
4.3. EBNF.822-address <-> MTS.ORAddress
This section defines the basic address mapping.
4.3.1. X.400 encoded in RFC 822
This section defines how X.400 addresses are represented in RFC
822 addresses.
The std-or-address syntax is used to encode OR Address
information in the 822.local-part of EBNF.822-address. Where
there is an applicable equivalence mapping, further OR Address
information is associated with the 822.domain component. This
cannot be used in the general case, due to character set
problems, and to the variants of X.400 OR Addresses which use
different attribute types. The only way to encode the full
PrintableString character set in a domain is by use of the
822.domain-ref syntax (i.e. 822.atom). This is likely to cause
problems on many systems. The effective character set of domains
is in practice reduced from the RFC 822 set, by restrictions
imposed by domain conventions and policy [10], and by the EBNF
definition in SMTP.
A generic 822.address consists of a 822.local-part and a
sequence of 822.domains (e.g., <@domain1,@domain2:user@domain3>).
All except the 822.domain associated with the 822.local-part
(domain3 in this case) are considered to specify routing within
the RFC 822 world, and will not be interpreted by the gateway
(although they may have identified the gateway from within the
RFC 822 world).
The 822.domain associated with the 822.local-part
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identifies the gateway from within the RFC 822 world. This final
822.domain may be used to determine some number of OR Address
attributes, where this does not conflict with the first role.
RFC 822 routing to gateways will usually be set up to facilitate
the 822.domain being used for both purposes.
In the case that there is no applicable equivalence mapping,
all of the X.400 address is encoded in the 822.local-part and the
822.domain identifies the gateway to which the message is being
sent. This technique may be used by the RFC 822 user for any
X.400 address where the equivalence mapping is not known.
In the case that there is an applicable MCGAM, the maximum
number of attributes are encoded in the 822.domain. The
remaining attributes are encoded on the LHS, using the
EBNF.std-or-address syntax. For example:
/I=J/S=Linnimouth/GQ=5/@Marketing.Widget.COM
encodes the MTS.ORAddress consisting of:
MTS.CountryName = "TC"
MTS.AdministrationDomainName = "BTT"
MTS.OrganizationName = "Widget"
MTS.OrganizationalUnitNames.value = "Marketing"
MTS.PersonalName.surname = "Linnimouth"
MTS.PersonalName.initials = "J"
MTS.PersonalName.generation-qualifier = "5"
on the basis of an MCGAM pair between:
Domain: Widget.COM
OR Address: O="Widget", ADMD="BTT", C="TC"
Given the OR address, the domain Widget.COM is determined from
the equivalence mapping and the next component is determined
algorithmically to give Marketing.Widget.COM. The remaining
attributes are encoded on the LHS in 822.local-part.
There is a further mechanism to simplify the encoding of
common cases, where the only attributes to be encoded on the LHS
are (non-Teletex) Personal Name attributes which comply with the
restrictions of 4.1.2. To achieve this, the 822.local-part shall
be encoded as EBNF.encoded-pn. In the previous example, if the
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GenerationQualifier was not present in the OR Address, it would
map with the RFC 822 address: J.Linnimouth@Marketing.Widget.COM.
From the standpoint of the RFC 822 Message Transfer System,
the domain specification is used to route the message in the
standard manner. The standard domain mechanisms are used to
select appropriate gateways for the corresponding OR Address
space. It is the responsibility of the management that defines
the equivalence mapping to define routing in the manner which
will enable the message to be delivered.
4.3.2. RFC 822 encoded in X.400
The previous section showed a mapping from X.400 to RFC 822. In
the case where the mapping was symmetrical and based on the
equivalence mapping, this has also shown how RFC 822 is encoded
in the X.400. This equivalence cannot be used for all RFC 822
addresses.
The general case is mapped by use of domain defined
attributes. A (Printable String) Domain defined type "RFC-822"
is defined. The associated attribute value is an ASCII string
encoded according to Section 3.3.3 of this specification. The
interpretation of the ASCII string follows RFC 822, and RFC 1123
[10,16]. Domains shall always be fully qualified.
Other OR Address attributes will be used to identify a
context in which the OR Address will be interpreted. This might
be a Management Domain, or some part of a Management Domain which
identifies a gateway MTA. For example:
C = "GB"
ADMD = "GOLD 400"
PRMD = "UK.AC"
O = "UCL"
OU = "CS"
"RFC-822" = "Jimmy(a)WIDGET-LABS.CO.UK"
OR
C = "TC"
ADMD = "Wizz.mail"
PRMD = "42"
"rfc-822" = "postel(a)venera.isi.edu"
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Note in each case the PrintableString encoding of "@" as "(a)".
In the second example, the "RFC-822" domain defined attribute is
interpreted everywhere within the (Private) Management Domain.
In the first example, further attributes are needed within the
Management Domain to identify a gateway. Thus, this scheme can
be used with varying levels of Management Domain co-operation.
There is a limit of 128 characters in the length of value of
a domain defined attribute, and an OR Address can have a maxmimum
of four domain defined attributes. Where the printable string
generated from the RFC 822 address exceeds 128 characters,
additional domain defined attributes are used to enable up to 512
characters to be encoded. These attributes shall be filled
completely before the next one is started. The (Printable
String) DDA keywords are: RFC822C1; RFC822C2; RFC822C3. Longer
addresses cannot be encoded.
MIXER defines a representation of RFC 822 addresses in
printable string domain defined attributes. Teletex domain
defined attributes with a key of RFC-822, RFC822C1; RFC822C2;
RFC822C3 shall not be generated. This is for backwards
compatibility reasons.
Reception of these attributes in the manner defined below is
mandatory. This is to allow the possibility for future versions
of MIXER to allow generation of teletex domain defined
attributes. Where the values of all of these teletex domain
defined attributes are printable string characters, they shall be
interpreted in the same way as the printable string domain
defined attributes. If this is not the case, the printable
string encoding translation shall be omitted. If both teletex
and printable string attributes are present, this is valid if and
only if they represent exactly the same RFC 822 address.
4.3.3. Component Ordering
In most cases, ordering of OR Address components is not
significant for the mappings specified. However, Organizational
Units (printable string and teletex forms) and Domain Defined
Attributes are specified as SEQUENCE in MTS.ORAddress, and so
their order may be significant. This specification needs to take
account of this:
1. To allow consistent mapping into the domain hierarchy
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2. To ensure preservation of order over multiple mappings.
There are three places where an order is specified:
1. The text encoding (std-or-address) of MTS.ORAddress as used
in the local-part of an RFC 822 address. An order is needed
for those components which may have multiple values
(Organizational Unit, and Domain Defined Attributes). When
generating an 822.std-or-address, components of a given type
shall be in hierarchical order with the most significant
component on the RHS (right hand side or domain part). If
there is an Organization Attribute, it shall be to the right
of any Organizational Unit attributes. These requirements
are for the following reasons:
- Alignment to the hierarchy of other components in RFC
822 addresses (thus, Organizational Units will appear
in the same order, whether encoded on the RHS or LHS).
- Backwards compatibility with RFC 987/1026.
- To ensure that gateways generate consistent addresses.
This is both to help end users, and to generate
identical message ids.
Further, it is recommended that all other attributes are
generated according to this ordering, so that all attributes
so encoded follow a consistent hierarchy. When generating
822.msg-id, this order shall be followed.
2. For the Organizational Units (OU) in MTS.ORAddress, the
first OU in the SEQUENCE is the most significant, as
specified in X.400.
3. For the Domain Defined Attributes in MTS.ORAddress, the
First Domain Defined Attribute in the SEQUENCE is the most
significant.
Note that although this ordering is mandatory for this
mapping, MIXER does not give additional implications on the
ordering significance within X.400.
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4.3.4. RFC 822 -> X.400 Basic Address Mapping
There are two basic cases:
1. X.400 addresses encoded in RFC 822. This will also include
RFC 822 addresses which are given reversible encodings.
2. "Genuine" RFC 822 addresses.
The mapping shall proceed as follows, by first assuming case 1).
STAGE I.
1. If the 822-address is not of the form:
local-part "@" domain
take the domain which will be routed on and apply step 2 of
stage 1 to derive (a possibly null) set of attributes. Then
go to stage II.
The gateway may reduce a source route address to this form
by removal of all but the last domain. In terms of the
design intentions of RFC 822, this would be an incorrect
action. (Note that an address of the form local%part@domain
is not a source route). However, in most cases, it will
provide a better service to the end user, and is in line
with the Internet Host Requirements. This is a reflection
on the common inappropriate use of source routing in RFC 822
based systems, despite the discussion in the Host
Requirements [10]. Either approach, or the intermediate
approach of stripping only domain references which reference
the local gateway are conformant to this specification.
2. If the 822.local-part uses the 822.quoted-string encoding,
remove this quoting. If the resulting unquoted
822.local-part has leading space, trailing space, or two
adjacent spaces go to stage II.
3. If the unquoted 822.local-part contains any characters not
in PrintableString, "{", "}", "*", and "$", go to stage II.
4. Parse the (unquoted) 822.local-part according to the EBNF
EBNF.std-or-address-input. Checking of upper bounds shall
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not be done at this point. If this parse fails, parse the
local-part according to the EBNF EBNF.encoded-pn. If this
parse fails, go to stage II. The result is a set of
type/value pairs.
5. Associate the EBNF.attribute-value syntax (determined from
the identified type) with each value, and check that it
conforms. If not, go to stage II.
6. If the set of attributes forms a valid X.400 address,
according to X.402, then go to step 9. All forms of X.400
address are allowed at this stage. Steps 7-8 default
attributes for certain types of OR Address.
7. If the set of attributes cannot form a mnemonic form of
X.400 address after addition of attributes which may be
derived from the EBNF.domain (C, ADMD, PRMD, O, OU), go to
stage II.
8. Attempt to parse EBNF.domain as:
*( domain-syntax "." ) known-domain
Where EBNF.known-domain is the longest possible match in the
set of MCGAMs being used by the gateway (described in
Section 4.2). EBNF.domain-syntax is the restricted domain
syntax defined in Section 4.2, to which all of the domain
components shall conform for the parse to be successful. If
this fails, go to stage II.
For each component, systematically allocate the attribute
implied by each EBNF.domain-syntax component in the order:
C, ADMD, PRMD, O, OU. Note that if the MCGAM used
identifies an "omitted attribute", then this attribute shall
be omitted in the systematic allocation. If this new
component exceed an upper bound (ADMD: 16; PRMD: 16; O: 64;
OU: 32) or it would lead to more than four OUs, then go to
stage II with the attributes derived.
The attributes derived in this step (referred to as RHS
attributes)
are merged with the ones derived from the LHS (step 6).
In some cases, not all of the RHF attributes are used. LHS
attributes are all used. C will not be in the LHS
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attributes. If ADMD is in the LHS attributes, only C is
taken from the RHS attributes. If PRMD is in the LHS
attributes, C and ADMD are taken from the RHS attributes.
If O is on the LHS, C, ADMD and PRMD (if present) are taken
from the RHS attributes. In other cases all RHS attributes
are taken.
9. Ensure that the set of attributes conforms both to the
MTS.ORAddress specification and to the restrictions on this
set given in X.400, and that no upper bounds are exceeded
for any attribute. If not go to stage II.
10. Build the OR Address from this information.
STAGE II.
This will only be reached if the RFC 822 EBNF.822-address is not
a valid X.400 encoding. This implies that the address refers to
a recipient on an RFC 822 system or that the encoding of the
address is invalid. Such addresses shall be encoded in an X.400
OR Address using a domain defined attribute.
1. Convert the EBNF.822-address to PrintableString, as
specified in Chapter 3.
2. Generate the "RFC-822" domain defined attribute from this
string.
3. Build the rest of the OR Address in the manner described
below.
It is not always possible to encode the domain defined attribute
due to length restrictions. If the limit is exceeded by a
mapping at the MTS level, then the gateway shall reject the
message in question. If this occurs at the IPMS level, then the
action will depend on the policy being taken for IPMS encoding,
which is discussed in Section 5.1.3.
Use Stage I, step 8, to generate a set of attributes to build the
remainder of the address. The administrative equivalence of the
mappings will ensure correct routing through X.400 to a gateway
back to RFC 822.
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If Stage I, step 8 does not generate a set of attributes or
the address generated is unroutable, the remained of the OR
address is generated as follows. The remainder of the OR address
effectively identifies a source route to a gateway from the X.400
side. There are three cases, which are handled differently:
SMTP Return Address
This shall be set up so that errors are returned through the
same gateway. Therefore, the OR Address of the local
gateway shall be used.
IPMS Addresses
These are optimised for replying. In general, the message
may end up anywhere within the X.400 world, and so this
optimisation identifies a gateway appropriate for the RFC
822 address being converted. The 822.domain to which the
address would be routed is used to select an appropriate
gateway.
In this case, it may be useful to use a non-local gateway,
which will optimise the reply address. This information
may be looked up in gateway tables in a manner equivalent to
the MCGAM lookup. Because of the similarity of lookup, the
three MCGAM lookup mechansims (table, X.500, DNS) are also
available to look up this information. This information is
local, and a gateway may insert any appropriate (gateway)
OR Address. The longest possible match on the 822.domain
defines which gateway to use. This mechanism is used for
any part of the X.400 namespace for which it is desirable to
identify a preferred X.400 gateway in order to optimise
routing.
If no mapping is found for the 822.domain, a default value
(typically that of the local gateway) is used. It is never
appropriate to ignore the locally used MCGAMs.
SMTP Recipient
As the RFC 822 and X.400 worlds are in principle fully
connected, there is no technical reason for this situation
to occur. In practice, this is not the case. In some cases,
routing may be configured to use X.400 to connect an RFC 822
island to the Internet. The information that this part of
the domain space is to be routed by X.400 rather than
remaining within the RFC 822 world shall be configured
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privately into the gateway in question. X.400 routing shall
not make use of the presence of the RFC-822 DDA to perform
X.400 routing. The OR address shall then be generated in
the same manner as for an IPMS address, using the locally
available MCGAMs. It is to support this case that the
definition of the global domain to gateway mapping is
important, as the use of this mapping will lead to a remote
X.400 address, which can be routed by X.400 routing
procedures. The information in this mapping shall not be
used as a basis for deciding to convert a message from RFC
822 to X.400.
Three examples are given, neither of which has applicable MCGAMs.
Example 1: (Address not in "localpart" "@" "domainpart")
@relay.co.uk:userb@host2
maps to
c=gb; a= ; p=uk.ac; o=mr; dd.rfc-822=(a)relay.co.uk:userb(a)host2;
Example 2: (Address with non printablestring characters)
Tom_Harris@cs.widget.com
maps to
c=us; a=MCI; P=relay; dd.rfc-822=Tom(u)Harris(a)cs.widget.com;
Example 3: (Address with an entry for alter.net into the OR Address
of Preferred Gateway table, pointing to c=gb; A=BTglobal; P=relay)
postmaster@UK.alter.net
maps to
c=gb; a=BTglobal; P=relay; dd.rfc-822=postmaster(a)UK.alter.net;
4.3.4.1. Heuristic for mapping RFC 822 to X.400
The following heuristic, which relates to ordering of address
components, may be used when mapping from RFC 822 to X.400. The
ordering of attributes may be inverted or mixed, and so the
following heuristics may be applied:
If there is an Organization attribute to the left of any Org
Unit attribute, assume that the hierarchy is inverted. This
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is to facilitate the situation where a user has input the
attributes in reverse hierarchical order. To do this the
gateway shall first map according to the order defined in
4.3.3. If this mapping generates an address which X.400
address verification shows to be invalid, this heuristic may
be applied as an alternative to immediate rejection of the
address.
4.3.5. X.400 -> RFC 822 Basic Address Mapping
There are two basic cases:
1. RFC 822 addresses encoded in X.400.
2. "Genuine" X.400 addresses. This may include symmetrically
encoded RFC 822 addresses.
When an MTS Recipient OR Address is interpreted, gatewaying will
be selected if there is a single "RFC-822" domain defined
attribute present. In this case, use mapping A and in other
cases, use mapping B.
RFC 1327 specified that this shall only be done when the
gateway identfied is local or otherwise known, and identified the
approach specified here as a pragmatic option. Experience has
shown that this is effective in practice, despite theoretical
problems.
If a gateway wishes to make a mapping in a manner similar to
RFC 1327, but does not wish for this global interpretation (e.g.,
to support an RFC 822 local system, which does not use global
addressing), then it may choose a private domain defined
attribute, different to "RFC-822". An RFC 1327 gateway might be
configurable to operate in this manner.
Mapping A
1. Map the domain defined attribute value to ASCII, as defined
in Chapter 3, and drop all other attributes.
Mapping B.
This is used for X.400 addresses which do not use the explicit
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RFC 822 encoding.
1. For all string encoded attributes, remove any leading or
trailing spaces, and replace adjacent spaces with a single
space.
The only attribute which is permitted to have zero length is
the ADMD. This shall be mapped onto a single space.
These transformations are for lookup only. If an
EBNF.std-or-address mapping is used as in 4), then the
original values shall be used.
2. The numeric country codes may be mapped to the two letter
values (as defined in ISO 3166). Global mappings are
usually only defined in terms of the ISO 3166 codes.
3. Noting the hierarchy specified in 4.3.1 and including
omitted attributes, determine the maximum set of attributes
which have an associated domain specification in the local
set of MCGAMs. If no match is found, allocate the domain as
described below, and go to step 5. The default domain to be
used is the specification of the local gateway. A gateway
may use other domains according to private mapping tables or
heuristics. For example, it may choose a domain which it
knows to provide a free gateway service to the mapped
address.
In cases where the address refers to an X.400 UA, it is
important that the generated domain will correctly route to
a gateway. In general, this is achieved by carefully co-
ordinating RFC 822 routing with the definition of the
MCGAMs, as there is no easy way for the gateway to make this
check. One rule that shall be used is that domains with
only one component will not route to a gateway. If the
generated domain does not route correctly, the address is
treated as if no match is found.
The gateway may also make use of a mapping equivalent to the
MCGAM mapping to determine the domain to use. This mapping
is done from the OR Address hierarchy. This is not a
global mapping, but is a routing style mapping from the OR
Address space, to enable a best choice domain to be
inserted. This mapping is supported by the three MCGAM
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lookup mechanisms.
4. The mapping identified in 3) gives a domain, and an OR
address prefix. Follow the hierarchy: C, ADMD, PRMD, O, OU.
For each successive component below the OR address prefix,
which conforms to the syntax EBNF.domain-syntax (as defined
in 4.3.1), allocate the next subdomain. At least one
attribute of the X.400 address shall not be mapped onto
subdomain, as 822.local-part cannot be null. If there are
omitted attributes in the OR address prefix, these will have
correctly and uniquely mapped to a domain component. Where
there is an attribute omitted below the prefix, all
attributes remaining in the OR address shall be encoded on
the LHS. This is to ensure a reversible mapping. For
example, if there is an address /S=XX/O=YY/ADMD=A/C=NN/ and
a mapping for /ADMD=A/C=NN/ is used, then /S=XX/O=YY/ is
encoded on the LHS.
5. If the address contains any attribute not used in mnemonic
form, then all of the attributes in the address shall be
encoded on the LHS in EBNF.std-or-address syntax, as
described below.
For addresses of mnemonic form, if the remaining components
are personal-name components, conforming to the restrictions
of 4.2.1, then EBNF.encoded-pn is derived to form
822.local-part. In other cases the remaining components are
simply encoded as 822.local-part using the
EBNF.std-or-address syntax. If necessary, the
822.quoted-string encoding is used. The following are
examples of legal quoting: "a b".c@x; "a b.c"@x. Either
form may be generated. Generation of the latter style is
strongly recommended.
Four examples are given.
Example 1: (Address with missing X.400 elements and no specific
mapping rule for "o=sales; a=Master400; C=it", where a mapping
exists for a=master400; C-it;)
S=Support; O=sales; A=Master400; C=it;
maps to
/S=Support/o=sales/@Master400.it
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Example 2: (Address with illegal characters in RFC822 generated
domain if default hierarchical translation (specific mapping rule
is existing for c=fr; a=atlas; p=autoroutes) is used)
S=renseignements; O=Region Parisienne; P=autoroutes; A=atlas; C=fr;
maps to
"/S=renseignements/o=Region Parisienne/"@autoroutes.fr
Example 3: (Address containing elements not mappable into RFC822
local part)
S=Rossi; DD.cap=20100; DD.ph1=Via Larga 11;
DDA.city=Milano; A=PtPostel; C=it;
maps to
"/DD.cap=20100/DD.ph1=Via Larga 11/DD.city=Milano/S=Rossi/"@ptpostel.it
Example 4: (Address with an entry for A=ATT; C=us; into the domain
of Preferred Gateway table, pointing to attmail.com)
G=Andy; S=Wharol; O=MMNY; A=ATT; C=us;
maps to
/G=Andy/S=Wharol/O=MMNY
4.4. Repeated Mappings
There are two types of repeated mapping:
1. A recursive mapping, where the repeat is within one gateway
2 A source route, where the repetition occurs across multiple
gateways
4.4.1. Recursive Mappings
It is possible to supply an address which is recursive at a
single gateway. For example:
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C = "XX"
ADMD = "YY"
O = "ZZ"
"RFC-822" = "Smith(a)ZZ.YY.XX"
This is mapped first to an RFC 822 address, and then back to the
X.400 address:
C = "XX"
ADMD = "YY"
O = "ZZ"
Surname = "Smith"
In some situations this type of recursion may be frequent. It is
important where this occurs, that no unnecessary protocol
conversion occurs. This will minimise loss of service.
4.4.2. Source Routes
The mappings defined are symmetrical and reversible across a
single gateway. The symmetry is particularly useful in cases of
(mail exploder type) distribution list expansion. For example,
an X.400 user sends to a list on an RFC 822 system which he
belongs to. The received message will have the originator and
any 3rd party X.400 OR Addresses in correct format (rather than
doubly encoded). In cases (X.400 or RFC 822) where there is
common agreement on gateway identification, then this will apply
to multiple gateways.
When a message traverses multiple gateways, the mapping will
always be reversible, in that a reply can be generated which will
correctly reverse the path. In many cases, the mapping will also
be symmetrical, which will appear clean to the end user. For
example, if countries "AB" and "XY" have RFC 822 networks, but
are interconnected by X.400, the following may happen: The
originator specifies:
Joe.Soap@Widget.PTT.XY
This is routed to a gateway, which generates:
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C = "XY"
ADMD = "PTT"
PRMD = "Griddle MHS Providers"
Organization = "Widget Corporation"
Surname = "Soap"
Given Name = "Joe"
This is then routed to another gateway where the mapping is
reversed to give:
Joe.Soap@Widget.PTT.XY
Here, use of the gateway is transparent.
Mappings will only be symmetrical where mapping equivalences
are defined. In other cases, the reversibility is more important,
due to the (far too frequent) cases where RFC 822 and X.400
services are partitioned.
The syntax may be used to source route. THIS IS STRONGLY
DISCOURAGED. For example:
X.400 -> RFC 822 -> X.400
C = "UK"
ADMD = "Gold 400"
PRMD = "UK.AC"
"RFC-822" = "/PN=Duval/DD.Title=Manager/(a)Inria.ATLAS.FR"
This will be sent to an arbitrary UK Academic Community gateway
by X.400. Then it will be sent by JNT Mail to another gateway
determined by the domain Inria.ATLAS.FR (FR.ATLAS.Inria). This
will then derive the X.400 OR Address:
C = "FR"
ADMD = "ATLAS"
PRMD = "Inria"
PN.S = "Duval"
"Title" = "Manager"
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Similarly:
RFC 822 -> X.400 -> RFC 822
"/RFC-822=jj(a)seismo.css.gov/PRMD=AC/ADMD=BT/C=GB/"@monet.berkeley.edu
This will be sent to monet.berkeley.edu by RFC 822, then to the
AC PRMD by X.400, and then to jj@seismo.css.gov by RFC 822.
4.5. Directory Names
Directory Names are an optional part of OR Name, along with OR
Address. The RFC 822 addresses are mapped onto the OR Address
component. As there is no functional mapping for the Directory
Name on the RFC 822 side, a textual mapping is used. There is no
requirement for reversibility in terms of the goals of this
specification. There may be some loss of functionality in terms
of third party recipients where only a directory name is given,
but this seems preferable to the significant extra complexity of
adding a full mapping for Directory Names.
The Directory Name shall be represented within an RFC 822
comment using the comaptible formats of RFC 1484 or RFC 1485. It
is recommended that the directory string format of RFC 1485 is
used [24]. The User Friendly Name form of RFC 1484 may be used
[25].
4.6. MTS Mappings
The basic mappings at the MTS level are:
1) SMTP originator ->
MTS.PerMessageSubmissionFields.originator-name
MTS.OtherMessageDeliveryFields.originator-name ->
SMTP originator
2) SMTP recipient ->
MTS.PerRecipientMessageSubmissionFields
MTS.OtherMessageDeliveryFields.this-recipient-name ->
SMTP recipient
SMTP recipients and return addresses are encoded as
EBNF.822-address.
The MTS Originator is always encoded as MTS.OriginatorName,
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which maps onto MTS.ORAddressAndOptionalDirectoryName, which in
turn maps onto MTS.ORName.
4.6.1. RFC 822 -> X.400 MTS Mappings
From the SMTP Originator, use the basic ORAddress mapping, to
generate MTS.PerMessageSubmissionFields.originator-name
(MTS.ORName), without a DirectoryName.
For recipients, the following settings are made for each
component of MTS.PerRecipientMessageSubmissionFields.
recipient-name
This is derived from the SMTP recipient by the basic
ORAddress mapping.
originator-report-request
This may either be set to "delivery-report", or set
according to SMTP extensions as set out in Appendix A.
explicit-conversion
This optional component is omitted, as this service is not
needed
extensions
The default value (no extensions) is used
4.6.2. X.400 -> RFC 822 MTS Mappings
The basic functionality is to generate the SMTP originator and
recipients. There is information present on the X.400 side,
which cannot be mapped into analogous SMTP services. For this
reason, new RFC 822 fields are added for the MTS Originator and
Recipients. The information discarded at the SMTP level will be
present in these fields. In some cases a (positive) delivery
report will be generated.
4.6.2.1. SMTP Mappings
Use the basic ORAddress mapping, to generate the SMTP originator
(return address) from
MTS.OtherMessageDeliveryFields.originator-name (MTS.ORName). If
MTS.ORName.directory-name is present, it is discarded. (Note
that it will be presented to the user, as described in 4.6.2.2).
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The mapping uses the MTA level information, and maps each
value of MTA.PerRecipientMessageTransferFields.recipient-name,
where the responsibility bit is set, onto an SMTP recipient.
Note:The SMTP recipient is conceptually generated from
MTS.OtherMessageDeliveryFields.this-recipient-name. This is
done by taking
MTS.OtherMessageDeliveryFields.this-recipient-name, and
generating an SMTP recipient according to the basic
ORAddress mapping, discarding MTS.ORName.directory-name if
present. However, if this model was followed exactly, there
would be no possibility to have multiple SMTP recipients on
a single message. This is unacceptable, and so layering is
violated.
4.6.2.2. Generation of RFC 822 Headers
Not all per-recipient information can be passed at the SMTP
level. For this reason, two new RFC 822 headers are created, in
order to carry this information to the RFC 822 recipient. These
fields are "X400-Originator:" and "X400-Recipients:".
The "X400-Originator:" field is set to the same value as the
SMTP originator. In addition, if
MTS.OtherMessageDeliveryFields.originator-name (MTS.ORName)
contains MTS.ORName.directory-name then this Directory Name shall
be represented in an 822.comment.
Recipient names, taken from each value of
MTS.OtherMessageDeliveryFields.this-recipient-name and
MTS.OtherMessageDeliveryFields.other-recipient-names are made
available to the RFC 822 user by use of the "X400-Recipients:"
field. By taking the recipients at the MTS level, disclosure of
recipients will be dealt with correctly. However, this conflicts
with a desire to optimise mail transfer. There is no problem
when disclosure of recipients is allowed. Similarly, there is no
problem if there is only one RFC 822 recipient, as the
"X400-Recipients" field is only given one address.
There is a problem if there are multiple RFC 822 recipients,
and disclosure of recipients is prohibited. In this case,
discard the per-recipient information.
If any MTS.ORName.directory-name is present, it shall be
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represented in an 822.comment.
If
MTS.OtherMessageDeliveryFields.orignally-intended-recipient-name
is present, then there has been redirection, or there has been
distribution list expansion. Distribution list expansion is a
per-message option, and the information associated with this is
represented by the "DL-Expansion-History:" field described in
Section 5.3.6. Other information is represented in an
822.comment associated with
MTS.OtherMessageDeliveryFields.this-recipient-name, The message
may be delivered to different RFC 822 recipients, and so several
addresses in the "X400-Recipients:" field may have such comments.
The non-commented recipient is the RFC 822 recipient. The EBNF of
the comment is defined by redirect-comment.
redirect-comment = redirect-first *( redirect-subsequent )
redirect-first = "Originally To:" mailbox "Redirected on"
date-time "To:" redirection-reason
redirect-subsequent = mailbox "Redirected Again on"
date-time "To:" redirection-reason
redirection-history-item = "intended recipient" mailbox
"redirected to" redirection-reason
"on" date-time
redirection-reason =
"Recipient Assigned Alternate Recipient"
/ "Originator Requested Alternate Recipient"
/ "Recipient MD Assigned Alternate Recipient"
/ "Directory Look Up"
/ "Alias"
It is derived from
MTA.PerRecipientMessageTransferFields.extension.redirection-history.
The values are taken from the X.400(92) Implementor's guide
(Version 13, July 1995). The first three values are in
X.400(88). The fourth value is in X.400(92), but has the name
"recipient-directory-substitution-alternate-recipient". An
example of this with two redirects is:
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X400-Recipients: postmaster@widget.com (Originally To:
sales-manager@sales.widget.com
Redirected on Thu, 30 May 91 14:39:40 +0100
To: Originator Requested Alternate Recipient
postmaster@sales.widget.com
Redirected Again on Thu, 30 May 91 14:41:20 +0100
To: Recipient MD Assigned Alternate Recipient)
In addition the following per-recipient services from
MTS.OtherMessageDeliveryFields.extensions are represented in
comments if they are used. None of these services can be
provided on RFC 822 networks, and so in general these will be
informative strings associated with other MTS recipients. In some
cases, string values are defined. For the remainder, the string
value shall be chosen by the implementor. If the parameter has
a default value, then no comment shall be inserted when the
parameter has that default value.
requested-delivery-method
physical-forwarding-prohibited
"(Physical Forwarding Prohibited)".
physical-forwarding-address-request
"(Physical Forwarding Address Requested)".
physical-delivery-modes
registered-mail-type
recipient-number-for-advice
physical-rendition-attributes
physical-delivery-report-request
"(Physical Delivery Report Requested)".
proof-of-delivery-request
"(Proof of Delivery Requested)".
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4.6.2.3. Delivery Report Generation
If SMTP is used, the behaviour is specified in Appendix A. In
other cases, if
MTA.PerRecipientMessageTransferFields.per-recipient-indicators
requires a positive delivery notification, this shall be
generated by the gateway. Supplementary Information shall be set
to indicate that the report is gateway generated. This
information shall include the name of the gateway generating the
report.
4.6.3. Message IDs (MTS)
A mapping from 822.msg-id to MTS.MTSIdentifier is defined. The
reverse mapping is not needed, as MTS.MTSIdentifier is always
mapped onto new RFC 822 fields. The value of
MTS.MTSIdentifier.local-part will facilitate correlation of
gateway errors.
To map from 822.msg-id, apply the standard mapping to
822.msg-id, in order to generate an MTS.ORAddress. The Country,
ADMD, and PRMD components of this are used to generate
MTS.MTSIdentifier.global-domain-identifier.
MTS.MTSIdentifier.local-identifier is set to the 822.msg-id,
including the braces "<" and ">". If this string is longer than
MTS.ub-local-id-length (32), then it is truncated to this length.
The reverse mapping is not used in this specification. It
would be applicable where MTS.MTSIdentifier.local-identifier is
of syntax 822.msg-id, and it algorithmically identifies
MTS.MTSIdentifier.
4.7. IPMS Mappings
All RFC 822 addresses are assumed to use the 822.mailbox syntax.
This includes all 822.comments associated with the lexical tokens
of the 822.mailbox. In the IPMS OR Names are encoded as
MTS.ORName. This is used within the IPMS.ORDescriptor,
IPMS.RecipientSpecifier, and IPMS.IPMIdentifier. An asymmetrical
mapping is defined between these components.
4.7.1. RFC 822 -> X.400
To derive IPMS.ORDescriptor from an RFC 822 address.
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1. Take the address, and extract an EBNF.822-address. Any
source routing shall be removed. This can be derived
trivially from either the 822.addr-spec or 822.route-addr
syntax. This is mapped to MTS.ORName as described above,
and used as IMPS.ORDescriptor.formal-name.
2. A string shall be built consisting of (if present):
- The 822.phrase component if the 822.address is an
822.phrase 822.route-addr construct.
- Any 822.comments, in order, retaining the parentheses.
This string is then encoded into T.61 using a human oriented
mapping (as described in Section 3.5). If the string is not
null, it is assigned to IPMS.ORDescriptor.free-form-name.
3. IPMS.ORDescriptor.telephone-number is omitted.
If IPMS.ORDescriptor is being used in IPMS.RecipientSpecifier,
IPMS.RecipientSpecifier.reply-request and
IPMS.RecipientSpecifier.notification-requests are set to default
values (false and none).
If the 822.group construct is present, any included
822.mailbox is encoded as above to generate a separate
IPMS.ORDescriptor. The 822.group is mapped to T.61 (as
described in Section 3.5), and a IPMS.ORDescriptor with only an
free-form-name component built from it.
4.7.2. X.400 -> RFC 822
Mapping from IPMS.ORDescriptor to RFC 822 address. In the basic
case, where IPMS.ORDescriptor.formal-name is present, proceed as
follows.
1. Encode IPMS.ORDescriptor.formal-name (MTS.ORName) as
EBNF.822-address.
2a. If IPMS.ORDescriptor.free-form-name is present, convert it
to ASCII or T.61 (Section 3.5), and use this as the
822.phrase component of 822.mailbox using the 822.phrase
822.route-addr construct.
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2b. If IPMS.ORDescriptor.free-form-name is absent. If
EBNF.822-address is parsed as 822.addr-spec use this as the
encoding of 822.mailbox. If EBNF.822-address is parsed as
822.route 822.addr-spec, then an 822.phrase taken from
822.local-part is added.
3 If IPMS.ORDescriptor.telephone-number is present, this is
placed in an 822.comment, with the string "Tel ". The
normal international form of number is used. For example:
(Tel +44-181-333-7777)
4. If IPMS.ORDescriptor.formal-name.directory-name is present,
then a text representation is placed in a trailing
822.comment.
5. If IPMS.RecipientSpecifier.report-request has any non-
default values, then an 822.comment "(Receipt Notification
Requested)", and/or "(Non Receipt Notification Requested)",
and/or "(IPM Return Requested)" may be appended to the
address. "(Receipt Notification Requested)" may be used to
infer "(Non Receipt Notification Requested)". The effort of
correlating P1 and P2 information is too great to justify
the gateway sending Receipt Notifications.
In RFC 1327, inclusion of these comments was mandatory.
Experience has shown that the clutter and confusion caused
to RFC 822 users does not justify the information conveyed.
Implementors are recommended to not include these comments.
Unless an application is found where retention of these
comments is desirable, they will be dropped from the next
version.
6. If IPMS.RecipientSpecifier.reply-request is True, an
822.comment "(Reply requested)" is appended to the address.
If IPMS.ORDescriptor.formal-name is absent,
IPMS.ORDescriptor.free-form-name is converted to ASCII (see
section 3.5), and used as 822.phrase within the RFC 822 822.group
syntax. For example:
Free Form Name ":" ";"
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Steps 3-6 are then followed.
4.7.3. IP Message IDs
There is a need to map both ways between 822.msg-id and
IPMS.IPMIdentifier. This allows for X.400 Receipt Notifications,
Replies, and Cross References to reference an RFC 822 Message ID,
which is preferable to a gateway generated ID. A reversible and
symmetrical mapping is defined. This provides fully reversible
mappings when messages pass multiple times across the X.400/RFC
822 boundary.
An important issue with messages identifiers is mapping to
the exact form, as many systems use these ids as uninterpreted
keys. The use of table driven mappings is not always
symmetrical, particularly in the light of alternative domain
names, and alternative management domains. For this reason, a
purely algorithmic mapping is used. A mapping which is simpler
than that for addresses can be used for two reasons:
- There is no major requirement to make message IDs "natural"
- There is no issue about being able to reply to message IDs.
(For addresses, creating a return path which works is more
important than being symmetrical).
The mapping works by defining a way in which message IDs
generated on one side of the gateway can be represented on the
other side in a systematic manner. The mapping is defined so
that the possibility of clashes is low enough to be treated as
impossible.
4.7.3.1. 822.msg-id represented in X.400
IPMS.IPMIdentifier.user is omitted. The
IPMS.IPMIdentifier.user-relative-identifier is set to a printable
string encoding of the 822.msg-id with the angle braces ("<" and
">") removed. The upper bound on this component is 64. The
options for handling this are discussed in Section 5.1.3.
4.7.3.2. IPMS.IPMIdentifier represented in RFC 822
The 822.domain of 822.msg-id is set to the value "MHS". The
822.local-part of 822.msg-id is constructed by building a string
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of syntax EBNF.id-loc from IPMS.IPMIdentifier.
id-loc ::= [ printablestring ] "*" [ std-or-address ]
EBNF.printablestring is the
IPMS.IPMIdentifier.user-relative-identifier, and EBNF.std-or-
address being an encoding of the IPMS.IPMIdentifier.user derived
according to this specification. 822.local-part is derived from
EBNF.id-loc, if necessary using the 822.quoted-string encoding.
For example:
<"147*/S=Dietrich/O=Siemens/ADMD=DBP/C=DE/"@MHS>
4.7.3.3. 822.msg-id -> IPMS.IPMIdentifier
If the 822.local-part can be parsed as:
[ printablestring ] "*" [ std-or-address ]
and the 822.domain is "MHS", then this ID was X.400 generated.
If EBNF.printablestring is present, the value is assigned to
IPMS.IPMIdentifier.user-relative-identifier. If
EBNF.std-or-address is present, the OR Address components derived
from it are used to set IPMS.IPMIdentifier.user.
Otherwise, this is an RFC 822 generated ID. In this case,
set IPMS.IPMIdentifier.user-relative-identifier to a printable
string encoding of the 822.msg-id without the angle braces and
omit IPMS.IPMID.user.
4.7.3.4. IPMS.IPMIdentifier -> 822.msg-id
If IPMS.IPMIdentifier.user is absent, and
IPMS.IPMIdentifier.user-relative-identifier mapped to ASCII and
angle braces added parses as 822.msg-id, then this is an RFC 822
generated ID.
Otherwise, the ID is X.400 generated. Use the
IPMS.IPMIdentifier.user to generate an EBNF.std-or-address form
string. Build the 822.local-part of the 822.msg-id with the
syntax:
[ printablestring ] "*" [ std-or-address ]
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The printablestring is taken from
IPMS.IPMIdentifier.user-relative-identifier. Use
822.quoted-string if necessary. The 822.msg-id is generated with
this 822.local-part, and "MHS" as the 822.domain.
4.7.3.5. Phrase form
In "In-Reply-To:" and "References:", the encoding 822.phrase may
be used as an alternative to 822.msg-id. To map from 822.phrase
to IPMS.IPMIdentifier, assign
IPMS.IPMIdentifier.user-relative-identifier to the phrase. When
mapping from IPMS.IPMIdentifier for "In-Reply-To:" and
"References:", if IPMS.IPMIdentifier.user is absent and
IPMS.IPMIdentifier.user-relative-identifier does not parse as
822.msg-id, generate an 822.phrase rather than adding the domain
MHS.
4.7.3.6. RFC 987 backwards compatibility
The mapping defined here is different to that used in RFC 987, as
the RFC 987 mapping lead to changed message IDs in many cases.
Fixing the problems is preferable to retaining backwards
compatibility. An implementation of this standard may recognise
message IDs generated by RFC 987. This is not recommended.
RFC 987 generated encodings may be recognised as follows.
When mapping from X.400 to RFC 822, if the
IPMS.IPMIdentifier.user-relative-identifier is "RFC-822" the id
is RFC 987 generated. When mapping from RFC 822 to X.400, if the
822.domain is not "MHS", and the 822.local-part can be parsed as
[ printablestring ] "*" [ std-or-address ]
then it is RFC 987 generated. In each of these cases, it is
recommended to follow the RFC 987 rules.
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Chapter 5 - Detailed Mappings
This chapter specifies detailed mappings for the functions
outlined in Chapters 1 and 2. It makes extensive use of the
notations and mappings defined in Chapters 3 and 4.
5.1. RFC 822 -> X.400: Detailed Mappings
The mapping of RFC 822/MIME messages to X.400 InterPersonal
Messages is described in Sections 5.1.1 to 5.1.7. Mapping of
NOTARY format delivery status notifications, which are all
messages of type multipart/report and subtype
delivery-status-notifications to X.400 delivery reports is
covered in Section 5.1.8.
5.1.1. Basic Approach
A single IP Message is generated from an RFC 822 message. The
RFC 822 headers are used to generate the IPMS.Heading.
Some RFC 822 fields cannot be mapped onto a standard IPM
Heading field, and so an extended field is defined in Section
5.1.2. This is then used for fields which cannot be mapped onto
existing services.
The message is submitted to the MTS, and the services
required can be defined by specifying
MTS.MessageSubmissionEnvelope. A few parameters of the MTA
Abstract service are also specified, which are not in principle
available to the MTS User. Use of these services allows RFC 822
MTA level parameters to be carried in the analogous X.400 service
elements. The advantages of this mapping far outweigh the
layering violation.
5.1.2. X.400 Extension Field
An IPMS Extension is defined:
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rfc-822-field HEADING-EXTENSION
VALUE RFC822FieldList
::= id-rfc-822-field-list
RFC822FieldList ::= SEQUENCE OF RFC822Field
RFC822Field ::= IA5String
The Object Identifier id-rfc-822-field-list is defined in
Appendix D.
To encode any RFC 822 Header using this extension, an
RFC822Field element is built using the 822.field omitting the
trailing CRLF (e.g., "Fruit-Of-The-Day: Kiwi Fruit"). All fields
shall be unfolded. There shall be no space before the ":". The
reverse mapping builds the RFC 822 field in a straightforward
manner. This RFC822Field is appended to the RFC822FieldList,
which is added to the IPM Heading as an extension field.
5.1.3. Generating the IPM
The IPM (IPMS Service Request) is generated according to the
rules of this section. The IPMS.IPM.body is generated from the
RFC 822 message body in the manner described in Section 5.1.5.
If no specific 1988 features are used, the IPM generated is
encoded as content type 2. Otherwise, it is encoded as content
type 22. The latter will always be the case if extension heading
fields are generated.
When generating the IPM, the issue of upper bounds are
handled as follows. Truncate fields to the upper bounds specified
in X.400. This will prevent problems with UAs which enforce
upper bounds, but will sometimes discard useful information.
This approach will cause more problems for some fields than
others (e.g., truncating an OR Address component that would be
used to route a reply would be a more severe problem than
truncating a Free Form Name). If the Free Form name is
truncated, it shall be done so that it does not break RFC 822
comments and RFC 1522 encoding.
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Note:This approach removes a choice of options given in RFC 1327,
based on operational experience.
The rest of this section concerns IPMS.IPM.heading
(IPMS.Heading). The only mandatory component of IPMS.Heading is
the IPMS.Heading.this-IPM (IPMS.IPMIdentifier). A default is
generated by the gateway. With the exception of "Received:", the
values of multiple fields are merged (e.g., If there are two
"To:" fields, then the mailboxes of both are merged to generate a
single list which is used in the IPMS.Heading.primary-recipients.
Information shall be generated from the standard RFC 822 Headers
as follows:
Date:
Ignore (Handled at MTS level)
Received:
Ignore (Handled at MTA level)
Message-Id:
Mapped to IPMS.Heading.this-IPM. For these, and all other
fields containing 822.msg-id the mappings of Chapter 4 are
used for each 822.msg-id.
From:
If Sender: is present, this is mapped to
IPMS.Heading.authorizing-users. If not, it is mapped to
IPMS.Heading.originator. For this, and other components
containing addresses, the mappings of Chapter 4 are used for
each address.
Sender:
Mapped to IPMS.Heading.originator. Because X.400 does not
have the same From/Sender distinction as RFC 822, this
mapping is not always natural and may lead to unexpected
results in some cases.
Reply-To:
Mapped to IPMS.Heading.reply-recipients.
To: Mapped to IPMS.Heading.primary-recipients
Cc: Mapped to IPMS.Heading.copy-recipients.
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Bcc: Mapped to IPMS.Heading.blind-copy-recipients if there is at
least one BCC: recipient. If there are no recipients in
this field, it shall either be mapped to a zero length
sequence or mapped to a single recipient that has a free
from name "BCC" and no other addressing information. This
alternate treatment is allowed because some X.400 systems
cannot handle a zero lenght sequence of addresses.
In-Reply-To:
If there is one value, it is mapped to
IPMS.Heading.replied-to-IPM, using the 822.phrase or
822.msg-id mapping as appropriate. If there are multiple
values, this cannot be done as the X.400 heading is single
valued. In this case no IPMS.Heading.replied-to-IPM is
generated and the values are mapped to
IPMS.Heading.related-IPMs, along with any values from a
"References:" field.
References:
Mapped to IPMS.Heading.related-IPMs.
Keywords:
Mapped onto a heading extension.
Subject:
Mapped to IPMS.Heading.subject. The field-body uses the
human oriented mapping referenced in Section 3.3.4.
Comments:
Mapped onto a heading extension.
This is a change from 1327, which specified to generate an
IPMS.BodyPart of type IPMS.IA5TextBodyPart with
IPMS.IA5TextBodyPart.parameters.repertoire set to the
default (ia5), containing the value of the fields, preceded
by the string "Comments: " and that this body part shall
precede the other one. Experience has shown that this
complexity is not justified. This text is retained to
facilitate backwards compatibility.
Encrypted:
Mapped onto a heading extension.
Resent-*
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Mapped onto a heading extension.
Note that it would be possible to use a ForwardedIPMessage
for these fields, but the semantics are (arguably) slightly
different, and it is probably not worth the effort.
Content-Language:
This field is defined in RFC 1766 [7]. Map the first two
characters of each value given onto the IPM Languages
extension. If any comments or values longer than two
characters occur, a header extension shall also be
generated.
Other Fields
In particular X-* fields, and "illegal" fields in common
usage (e.g., "Fruit-of-the-day:") are mapped onto a heading
extension, unless covered by another section or appendix of
this specification. The same treatment is applied to RFC
822 fields where the content of the field does not conform
to RFC 822 (e.g., a Date: field with unparseable syntax).
The mapping of the following headings is defined in RFC1494bis.
MIME-Version: 5
Content-Transfer-Encoding:
Content-Type
Content-ID
Content-Description
5.1.4. Generating the IPM Body
Generation of the IPM Body is defined in RFC1494bis.
5.1.5. Mappings to the MTS Abstract Service
The MTS.MessageSubmissionEnvelope comprises
MTS.PerMessageSubmissionFields, and
MTS.PerRecipientMessageSubmissionFields. The mandatory
parameters are defaulted as follows.
MTS.PerMessageSubmissionFields.originator-name
This is always generated from SMTP, as defined in Chapter 4.
MTS.PerMessageSubmissionFields.content-type
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Set to the value implied by the encoding of the IPM (2 or
22).
MTS.PerRecipientMessageSubmissionFields.recipient-name
These will always be supplied from SMTP, as defined in
Chapter 4.
Optional components are omitted, and default components
defaulted. This means that disclosure of recipients is
prohibited and conversion is allowed. There are two exceptions
to the defaulting. For
MTS.PerMessageSubmissionFields.per-message-indicators, the
following settings are made:
- Alternate recipient is allowed, as it seems desirable to
maximise the opportunity for (reliable) delivery.
If SMTP is used, Appendix A shall be followed in setting these
parameters.
The trace is set to indicate conversion (described below)
and the encoded information types in the trace is derived from
the message generated by the gateway, and shall reflect all body
parts (including those in enclosed messages). In addition it
shall include the Encoded Information Type "eit-mixer", which is
defined in Appendix D. The presence of the EIT will indicate to
the X.400 recipient that a MIXER conversion has occurred.
MTS.PerMessageSubmissionFields.original-encoded-information-types
will include all of the values used in the trace, unless
specified otherwise in RFC1494bis.
This type of conversion will prevent the normal loop
detection from working in certain circumstances, and introduces
the possiblity of gateway loops. MIXER gateways shall therefore
count the number of MIXER conversions made. If this count
exceeds five in one direction, the message shall be treated as if
a loop has been detected.
The MTS.PerMessageSubmissionFields.content-correlator is
encoded as IA5String, and contains the Subject:, Message-ID:,
Date:, and To: fields (if present) in this order. This
includes the strings "Subject:", "Date:", "To:", "Message-ID:",
and appropriate folding to make the field appear readable. This
shall be truncated to MTS.ub-content-correlator-length (512)
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characters. In addition, if there is a "Subject:" field, the
MTS.PerMessageSubmissionFields.content-identifier, is set to a
printable string representation of the contents of it. If the
length of this string is greater than MTS.ub-content-id-length
(16), it shall be truncated to 13 characters and the string "..."
appended. Both are used, due to the much larger upper bound of
the content correlator, and that the content id is available in
X.400(1984).
5.1.6. Mappings to the MTA Abstract Service
There is a need to map directly onto some aspects of the MTA
Abstract service, for the following reasons:
- So the MTS Message Identifier can be generated from the RFC
822 Message-ID:.
- So that the submission date can be generated from the
822.Date.
- To prevent loss of trace information
- To prevent RFC 822/X.400 looping caused by distribution
lists or redirects
The following mappings are defined.
Message-Id:
If this is present and no Resent: fields are present, the
MTA.PerMessageTransferFields.message-identifier may be
generated from it, using the mappings described in
Chapter 4.
This mapping arguably generates messages which do not
conform to US GOSIP (1984 version only), which states:
6.7.e MPDU Identifier Validation
(1) Validation of the GlobalDomainIdentifier component of
the MPDU Identifier is performed on reception of a message
(i.e. the result of a TRANSFER.Indication).
(2) The country name should be known to the validating
domain, and depending on the country name, validation of the
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ADMD name may also be possible.
(3) Additional validation of the GlobalDomainIdentifier is
performed against the corresponding first entry in the
TraceInformation. If inconsistencies are found during the
comparison, a non-delivery notice with the above defined
reason and diagnostic code is generated.
(4) A request will be generated to the CCITT for a more
meaningful diagnostic code (such as
"InconsistentMPUTIdentifier").
This applies to ADMDs only, and is specified in the 1984
version and not the 1988 version. Conformance depends on the
interpretation of "inconsistency". The specification makes the
most sensible choice, and so is not being changed in the update
from RFC 1327.
Date: (and Resent-Date:)
If one or more Resent-Date: fields is present, the most
recent Resent-Date: field shall be used instead of the Date:
field in the following description.
The Date: field is used to set the first component of
MTA.PerMessageTransferFields.trace-information
(MTA.TraceInformationElement). The SMTP originator is
mapped into an MTS.ORAddress, and used to derive
MTA.TraceInformationElement.global-domain-identifier. The
optional components of
MTA.TraceInformationElement.domain-supplied-information are
omitted, and the mandatory components are set as follows:
MTA.DomainSuppliedInformation.arrival-time
This is set to the date derived from Date:
MTA.DomainSuppliedInformation.routing-action
Set to relayed.
The first element of
MTA.PerMessageTransferFields.internal-trace-information is
generated in an analogous manner, although this can be
dropped later in certain circumstances (see the procedures
for "Received:"). The
MTA.InternalTraceInformationElement.mta-name is derived from
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the 822.domain in the 822 MTS Originator address.
Received:
All RFC 822 trace is used to derive
MTA.PerMessageTransferFields.trace-information and
MTA.PerMessageTransferFields.internal-trace-information.
Processing of Received: lines follows processing of Date:,
and is done from the bottom to the top of the RFC 822 header
(i.e., in chronological order). When other trace elements
(in particular X400-Received:) are processed the relative
ordering (top to bottom of the header) shall be retained
correctly.
The initial element of
MTA.PerMessageTransferFields.trace-information shall be
generated from Date: as described above, unless the message
has previously been in X.400, when it will be derived from
the X.400 trace information.
For each Received: field, the following processing shall be
done. If the "by" part of the received is present and
there is an available MCGAM which can map this domain, use
it to derive an MTS.GlobalDomainIdentifier. Otherwise
MTS.GlobalDomainIdentifier is set from local information.
If this is different from the one in the last element of
MTA.PerMessageTransferFields.trace-information
(MTA.TraceInformationElement.global-domain-identifier)
create a new MTA.TraceInformationElement, and optionally
remove
MTA.PerMessageTransferFields.internal-trace-information.
Requirements on trace stripping are discussed below.
Then add a new element (MTA.InternalTraceInformationElement)
to MTA.PerMessageTransferFields.internal-trace-information,
creating this if needed. This shall be done, even if
inter-MD trace is created. The
MTA.InternalTraceInformationElement.global-domain-identifier
is set to the value derived. The
MTA.InternalTraceInformationElement.mta-supplied-information
(MTA.MTASuppliedInformation) is set as follows:
MTA.MTASuppliedInformation.arrival-time
Derived from the date of the Received: line
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MTA.MTASuppliedInformation.routing-action
Set to relayed
The MTA.InternalTraceInformationElement.mta-name is taken
from the "by" component of the "Received:" field, truncated
to MTS.ub-mta-name-length (32). For example:
Received: from computer-science.nottingham.ac.uk by
vs6.Cs.Ucl.AC.UK via Janet with NIFTP id aa03794;
28 Mar 89 16:38 GMT
Generates the string
vs6.Cs.Ucl.AC.UK
The gateway shall add in a single element of trace information,
reflecting the gateway's local information and the time of
conversion. The
MTA.InternalTraceInformationElement.mta-supplied-information
(MTA.MTASuppliedInformation) is set as follows:
MTA.DomainSuppliedInformation.arrival-time
Set to the time of conversion
MTA.DomainSuppliedInformation.routing-action
Set to relayed
MTA.AdditionalAcctions.converted-encoded-information-types
Set to correct set of EITs for the message that is generated
by the gateway. This trace element will thus reflect
gateway operation as a conversion.
This trace generation will often lead to generation of
substantial amounts of trace information, which does not reflect
X.400 transfers. Stripping of some of this trace may be
necessary in some operational environments. This stripping
shall be considered a function of the associated X.400 MTA, and
not of the MIXER gateway.
5.1.7. Mapping New Fields
This specification defines a number of new fields for Reports,
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Notifications and IP Messages. A gateway conforming to this
specification shall map all of these fields to X.400, except as
defined below.
The mapping of two extended fields is particularly
important, in order to prevent looping. "DL-Expansion-History:"
is mapped to
MTA.PerMessageTransferFields.extensions.dl-expansion-history
X400-Received: shall be mapped to
MTA.PerMessageTransferFields.trace-information and
MTA.PerMessageTransferFields.internal-trace-information. In
cases where X400-Received: is present, the usual mapping of Date:
to generate the first element of trace shall not be done. This
is because the message has come from X.400, and so the first
element of trace can be taken from the first X400-Received:.
The following fields shall not be mapped, and shall be
discarded:
- Discarded-X400-MTS-Extensions:
- Message-Type:
- Discarded-X400-IPMS-Extensions:
- X400-Content-Type:
- X400-Originator:
- X400-Recipients:
- X400-MTS-Identifier: Mapping this field would be useful in
some circumstances, but very dangerous in others (e.g.,
following an internet list expansion). Therefore it is not
mapped.
5.1.8. Mapping Delivery Status Notifications to X.400
5.1.8.1. Basic Model
Internet Mail delivery status notifications (DSN) are mapped to
X.400 delivery reports. With message mapping, information
without a mapping is carried by an IPM Extension. This cannot
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be done for delivery reports. Two mechanisms are used for
information where there is not a direct mapping.
The first mechanism is to define extensions, which allow all
of the DSN information to be carried in the delivery report.
This is not completely satisfactory for two reasons:
1. User defined extensions are supported by the ISO version of
the standard, but not the CCITT one. Therefore,
implementation support for these extensions will not be
universal.
2 X.400 User Agent implementations will not in general
recognise these extensions. Therefore, although the
information will be present, it will often not be available
to the user. This may be very problematic, as this
information may be critical to diagnosing the reason for a
failure.
Therefore a second mechanism is defined. This shall always
be used when the DSN contains non-delivery information, and may
be used in other cases. This mechanism is to map the whole DSN
(as if it were an ordinary multipart) into the return of content.
This will make the DSN information available as a text body part
in the outer message, with the real returned content as an
enclosed message. This mechanism will ensure that information is
not lost at the gateway.
5.1.8.2. DSN Extensions
Two X.400 MTS extensions are defined as follows:
dsn-header-list EXTENSION
RFC822FieldList
::= id-dsn-header-list
dsn-field-list EXTENSION
RFC822FieldList
::= id-dsn-field-list
The Object Identifiers id-dsn-header-list and id-dsn-field-list
are defined in Appendix D. Theses extensions are used in the
same way as the IPM extension rfc-822-field, described in Section
5.1.2. These extensions may only be used with ISO-10021, and
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not X.400 (which does not allow user extensions at the MTS
level).
5.1.8.3. DSN to Delivery Report Mapping
Some DSNs are mapped to Delivery Reports and some to IPMs,
according to the value of the action field. The mapping to an
IPM is exactly as for a normal IPM mapping. The choice of IPM
and Delivery report is made for each reported recipient. If
this choice is different for different reported recipients both a
Delivery Report and an IPM shall be generated.
Reports are not be submitted in the X.400 model, and so the
report submission is considered in terms of the MTA Abstract
Service. An MTA.Report is constructed. The
MTA.ReportTransferEnvelope.report-identifier is generated from
the Message-Id of the DSN (if present) and otherwise generated as
the MTA would generate one for a submitted message.
The DSN has an RFC 822 header. Trace is mapped in the same
manner as for a message to
MTA.ReportTransferEnvelope.trace-information. All other headers
are used to create a dsn-header-list extension, which is added to
MTA.PerReportTransferFields.extensions.
The DSN will have a single SMTP recipient. This is mapped
to the MTA.ReportTransferEnvelope.report-destination-name.
The DSN is then treated as a normal MIME message, and an
X.400 IPM is generated. This IPM is used as
MTA.PerReportTransferFields.returned-content, and its type is
used to set MTA.PerReportTransferFields.content-type. The DSN
body part is mapped as if it was IA5 text/plain.
The mandatory MTA.PerReportTransferFields.subject-identifier
shall be generated from the DSN.per-message-field
original-envelope-id, if this starts with the string
"X400-MTS-Identifier: ", and derived from the rest of the field,
which is encoded as EBNF.mts-msg-id. In other cases, this field
shall be generated by the MIXER Gateway.
All other mappings are made from the DSN body part. A dsn-
field-list extension is created and added to
MTA.ReportTransferFields.extensions. This is referred to as the
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per report extension list. The DSN.per-message-fields are mapped
as follows:
original-envelope-id-field
reporting-mta-field
dsn-gateway-field
received-from-mta-field
arrival-date-field
extension-field
other
All of these fields are added to the per report extension
list. Currently there are no other mappings defined.
Each reported recipient is considered in turn, and a
MTA.PerRecipientReportTransferFields created for each. The
parameters of this are defaulted as follows:
originally-specified-recipient-number
In general, these are not available, and so are assigned
incrementally.
last-trace-information
The arrival-time is generated from DSN.arrival-date if
present, and if not from the Date: of the DSN. This is a
strucutred field, and the Report element contains the key
information on the recipient. For a DeliveryReport, the
type-ofMTS-user is defaulted to public and the
message-deliery-time is set to the same as the arrival-time.
For a NonDeliveryReport, the code mappings are define in
Section 5.1.8.4.
A dsn-field-list extension is created and added to
MTA.PerRecipientTransferFields.extensions. This is referred to
as the per recipient extension list. The
DSN.per-recipient-fields are mapped as follows
original-recipient-field
Mapped to
MTA.PerRecipientReportTransferFields.originally-intended-recipient-name.
final-recipient-field
Mapped to
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MTA.PerRecipientReportTransferFields.actual-recipient-name.
action-field
If this is set to "failed", a non-delivery report is
generated. If this is set to "delivered" a delivery report
is generated. Bit one or two of
MTA.PerRecipientTransferFields.per-recipient-indicators is
set accordingly. This also controls the encoding of
MTA.PerRecipientTransferFields.last-trace-information, and
the selection of the report type.
For other values of the action-field ("delayed", "relayed",
"expanded"), an IPM is generated. This enables the status
information to be communicated to the X.400 user, without
the confusion of multiple delivery reports.
status-field
This is added to the per report extension list. For non-
delivery, it is also used to generate the reason and
diagnostic codes contained within
MTA.PerRecipientReportTransferFields.last-trace. The
mappings are defined below.
remote-mta-field
diagnostic-code-field
last-attempt-date-field
will-retry-until-field
extension-field
other
All of these fields are added to the per recipient extension
list.
5.1.8.4. Status Value Mappings
Status values are mapped to X.400 reason and diagnostic codes as
follows.
If a status value is found that is not in this table, the
gateway may use the same mapping as for "X.n.0" (1/None or
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0/None), or it may map to another, configurable code.
Implementors are requested to forward new codes to the mixer list
for inclusion in future versions of this standard. So for
instance. "5.2.37", currently undefined, would map onto the same
as "5.2.0", namely 1/None.
DSN code Meaning X400 code Meaning
X.0.0 Other status 1/None
X.1.0 Other Address Status 1/None
X.1.1 Bad mailbox address 1/0 Unrecognized
X.1.2 Bad system address 1/0 Unrecognized
X.1.3 Bad mailbox address syntax 1/0 Unrecognized
X.1.4 Mailbox address ambiguous 1/1
X.1.5 Only used for positive reports, not applicable
X.1.6 Destination mailbox has moved 1/43 New address unknown
X.1.7 Bad sender's mailbox address syntax 1/11 Invalid arguments
X.1.8 Bad sender's system address 1/11 Invalid arguments
X.2.0 Other or undefined mailbox status 1/None
X.2.1 Mailbox disabled, not accepting 1/4 Recipient unavailable
X.2.2 Mailbox full 1/4
X.2.3 Message length exceeds admin limit. 1/7 Content too long
X.2.4 Mailing list expansion problem 1/30 DL expansion failure
X.3.0 Other or undefined system status 0/None
X.3.1 System full 1/2 MTS congestion
X.3.2 System not accepting network messages 1/2 MTS congestion
X.3.3 System not capable of selected feat 1/18 Unsupp. crit. func
X.3.4 Message too big for system 1/7
X.3.5 System incorrectly configured 1/None
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X.4.0 Other or undefined network or routing 0/None
X.4.1 No answer from host 0/None
X.4.2 Bad connection 0/None
X.4.3 Routing server failure 6/None Directory op unsucc.
X.4.4. Unable to route 0/None
X.4.5 Network congestion 1/2 MTS congest.
X.4.6 Routing loop detected 1/3
X.4.7 Delivery time expired 1/5
X.5.0 Other or undefined protocol status 1/None
X.5.1 Invalid command 1/14 Protocol viol.
X.5.2 Syntax error 1/14
X.5.3 Too many recipients 1/16
X.5.4 Invalid command arguments 1/14
X.5.5 Wrong protocol version 1/18 Unsupp.crit.func
X.6.0 Other or undefined media error 2/None Conv. not perf
X.6.1 Media not supported 1/6 EIT unsupp.
X.6.2 Conversion required and prohibited 1/9
X.6.3 Conversion required but not supported 2/8
X.6.4 Conversion with loss performed POSITIVE only
X.6.5 Conversion failed 2/47 Unable to downgrade
X.7.0 Other or undefined security status 1/46
X.7.1 Delivery not authorized, message ref 1/29 No DL submit perm
X.7.2 Mailing list expansion prohibited 1/28
X.7.3 Security conversion req but not poss 1/46 Secure mess. error
X.7.4 Security features not supported 1/46
X.7.5 Cryptographic failure 1/46
X.7.6 Cryptographic algorithm not supported 1/46
X.7.7 Message integrity failure 1/46
5.1.8.5. DSNs that originated in X.400
The mapping of X.400 delivery reports to DSNs will in general
provide sufficient information to make a useful reverse mapping.
Messages will often be mapped multiple times, commonly due to
forwarding messages and to distribution lists. Multiple
mappings for delivery reports will be a good deal less common.
For this reason, the reverse mapping of the X.400 DSN extensions
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defined in MIXER is optional.
5.2. Return of Contents
RFC 1327 offered two approaches for return of content, as this
service is optional in X.400 and expected in RFC 822. MIXER
simply requires that a gateway requests the return of content
service from X.400.
5.3. X.400 -> RFC 822: Detailed Mappings
5.3.1. Basic Approach
A single RFC 822 message is generated from the incoming IP
Message, Report, or IP Notification. All IPMS.BodyParts are
mapped onto a single RFC 822 body. Other services are mapped
onto RFC 822 header fields. Where there is no appropriate
existing field, new fields are defined for IPMS, MTS and MTA
services.
The gateway mechanisms will correspond to MTS Delivery. As
with submission, there are aspects where the MTA (transfer)
services are also used. In particular, there is an optimisation
to allow for multiple SMTP recipients.
5.3.2. RFC 822 Settings
An RFC 822 Message has a number of mandatory fields in the RFC
822 Header. Some SMTP services mandate specification of an SMTP
Originator. Even in cases where this is optional, it is usually
desirable to specify a value. The following defaults are
defined, which shall be used if the mappings specified do not
derive a value:
SMTP Originator
If this is not generated by the mapping (e.g., for a
Delivery Report), a value pointing at a gateway
administrator shall be assigned.
Date:
A value will always be generated
From:
If this is not generated by the mapping, it is assigned
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equal to the SMTP Originator. If this is gateway generated,
an appropriate 822.phrase shall be added.
At least one recipient field
If no recipient fields are generated, a field "To: list:;",
shall be added.
This will ensure minimal RFC 822 compliance. When generating RFC
822 headers, folding may be used. It is recommended to do this,
following the guidelines of RFC 822.
5.3.3. Basic Mappings
5.3.3.1. Encoded Information Types
This mapping from MTS.EncodedInformationTypes is needed in
several disconnected places. EBNF is defined as follows:
encoded-info = 1#encoded-type
encoded-type = built-in-eit / object-identifier
built-in-eit = "Undefined" ; undefined (0)
/ "Telex" ; tLX (1)
/ "IA5-Text" ; iA5Text (2)
/ "G3-Fax" ; g3Fax (3)
/ "TIF0" ; tIF0 (4)
/ "Teletex" ; tTX (5)
/ "Videotex" ; videotex (6)
/ "Voice" ; voice (7)
/ "SFD" ; sFD (8)
/ "TIF1" ; tIF1 (9)
MTS.EncodedInformationTypes is mapped onto EBNF.encoded-info.
MTS.EncodedInformationTypes.non-basic-parameters is ignored.
Built in types are mapped onto fixed strings (compatible with
X.400(1984) and RFC 987), and other types are mapped onto
EBNF.object-identifier.
5.3.3.2. Global Domain Identifier
The following simple EBNF is used to represent
MTS.GlobalDomainIdentifier:
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global-id = std-or-address
This is encoded using the std-or-address syntax, for the
attributes within the Global Domain Identifier.
5.3.4. Mappings from the IP Message
Consider that an IPM has to be mapped to RFC 822. The IPMS.IPM
comprises an IPMS.IPM.heading and IPMS.IPM.body. The heading is
considered first. Some EBNF for new fields is defined:
ipms-field = "Supersedes" ":" 1*msg-id
/ "Expires" ":" date-time
/ "Reply-By" ":" date-time
/ "Importance" ":" importance
/ "Sensitivity" ":" sensitivity
/ "Autoforwarded" ":" boolean
/ "Incomplete-Copy" ":"
/ "Content-Language" ":" 1#language
/ "Message-Type" ":" message-type
/ "Discarded-X400-IPMS-Extensions" ":" 1#object-identifier
/ "Autosubmitted" ":" autosubmitted
importance = "low" / "normal" / "high"
sensitivity = "Personal" / "Private" /
"Company-Confidential"
language = 2*ALPHA [ "(" language-description ")" ]
language-description = printable-string
message-type = "Delivery Report"
/ "InterPersonal Notification"
/ "Multiple Part"
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autosubmitted = "not-auto-submitted"
/ "auto-generated"
/ "auto-replied"
/ "auto-forwarded"
The mappings and actions for the IPMS.Heading are now specified
for each element. Addresses and Message Identifiers are mapped
according to Chapter 4.
Other mappings are explained, or are straightforward
(algorithmic). If a field with addresses contains zero elements,
it shall be discarded, except for
IPMS.Heading.blind-copy-recipients, which can be mapped onto BCC:
(the only RFC 822 field which allows zero recipients).
IPMS.Heading.this-IPM
Mapped to "Message-ID:".
IPMS.Heading.originator
If IPMS.Heading.authorizing-users is present this is mapped
to Sender:, if not to "From:".
IPMS.Heading.authorizing-users
Mapped to "From:".
IPMS.Heading.primary-recipients
Mapped to "To:".
IPMS.Heading.copy-recipients
Mapped to "Cc:".
IPMS.Heading.blind-copy-recipients
Mapped to "Bcc:".
IPMS.Heading.replied-to-ipm
Mapped to "In-Reply-To:".
IPMS.Heading.obsoleted-IPMs
Mapped to the extended RFC 822 field "Supersedes:". The
replaces the RFC 1327 field "Obsoletes:". Reverse mapping
of the RFC 1327 field may be supported.
IPMS.Heading.related-IPMs
Mapped to "References:".
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IPMS.Heading.subject
Mapped to "Subject:". The contents are converted to ASCII
or T.61 (as defined in Section 3.5). CRLF will not be
present in a valid X.400 field. Any CRLF present are not
mapped, but are used as points at which the subject field
shall be folded, unless an RFC 1522 encoding is used.
IPMS.Heading.expiry-time
Mapped to the extended RFC 822 field "Expires:". The
replaces the RFC 1327 field "Expiry-Date:". Reverse
mapping of the RFC 1327 field may be supported.
IPMS.Heading.reply-time
Mapped to the extended RFC 822 field "Reply-By:".
IPMS.Heading.reply-recipients
Mapped to "Reply-To:".
IPMS.Heading.importance
Mapped to the extended RFC 822 field "Importance:".
IPMS.Heading.sensitivity
Mapped to the extended RFC 822 field "Sensitivity:".
IPMS.Heading.autoforwarded
Mapped to the extended RFC 822 field "Autoforwarded:".
The standard extensions (Annex H of X.420 / ISO 10021-7) are
mapped as follows:
incomplete-copy
Mapped to the extended RFC 822 field "Incomplete-Copy:".
language
Mapped to the RFC 822 field "Content-Language:", defined in
RFC 1766 [7]. This mapping may be made without loss of
information.
auto-submitted
Map to the extended RFC 822 field "Autosubmitted:".
If the RFC 822 extended header is found, this shall be
mapped onto an RFC 822 header, as described in Section 5.1.2.
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If a non-standard extension is found, it shall be discarded,
unless the gateway understands the extension and can perform an
appropriate mapping onto an RFC 822 header field. If extensions
are discarded, the list is indicated in the extended RFC 822
field "Discarded-X400-IPMS-Extensions:".
5.3.4.1. Mapping the IPMS Body
The mapping of the IPMS Body is defined in RFC 1494bis.
5.3.4.2. Example Message
An example message, illustrating a number of aspects is given
below.
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Received: from mhs-relay.ac.uk by bells.cs.ucl.ac.uk via JANET with NIFTP
id <7906-0@bells.cs.ucl.ac.uk>; Thu, 30 May 1991 18:24:55 +0100
X400-Received: by mta "mhs-relay.ac.uk" in /PRMD=uk.ac/ADMD= /C=gb/; Relayed;
Thu, 30 May 1991 18:23:26 +0100
X400-Received: by /PRMD=HMG/ADMD=GOLD 400/C=GB/; Relayed;
Thu, 30 May 1991 18:20:27 +0100
Message-Type: Multiple Part
Date: Thu, 30 May 1991 18:20:27 +0100
X400-Originator: Stephen.Harrison@gosip-uk.hmg.gold-400.gb
X400-MTS-Identifier:
[/PRMD=HMG/ADMD=GOLD 400/C=GB/;PC1000-910530172027-57D8]
Original-Encoded-Information-Types: ia5
X400-Content-Type: P2-1984 (2)
X400-Content-Identifier: Email Problems
From: Stephen.Harrison@gosip-uk.hmg.gold-400.gb (Tel +44 71 217 3487)
Message-ID: <PC1000-910530172027-57D8*@MHS>
To: Jim Craigie <NTIN36@gec-b.rutherford.ac.uk>,
Tony Bates <tony@ean-relay.ac.uk>,
Steve Kille <S.Kille@cs.ucl.ac.uk>
Subject: Email Problems
Sender: Stephen.Harrison@gosip-uk.hmg.gold-400.gb
MIME-Version: 1.0
Content-Type: multipart/mixed; boundary=boundary-1
--boundary-1
Content-Type: text/plain; charset=US-ASCII
Hope you gentlemen.......
Regards,
Stephen Harrison
UK GOSIP Project
..... continued on next page
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--boundary-1
Content-Type: message/rfc822
From: Urs Eppenberger <Eppenberger@verw.switch.ch>
Message-ID:
<562*/S=Eppenberger/OU=verw/O=switch/PRMD=SWITCH/ADMD=ARCOM/C=CH/@MHS>
To: "Stephen.Harrison" <Stephen.Harrison@gosip-uk.hmg.gold-400.gb>
Cc: kimura@bsdarc.bsd.fc.nec.co.jp
Subject: Response to Email link
Content-Type: multipart/mixed; boundary=boundary-2
--boundary-2
Dear Mr Harrison......
--boundary-2--
--boundary-1--
5.3.5. Mappings from an IP Notification
Because of the service setting, IP Notifications will not usually
need to be mapped by a MIXER gateway. A message is generated,
with the following fields:
From:
Set to the IPMS.IPN.ipn-originator.
To: Set to the recipient from MTS.MessageSubmissionEnvelope.
If there have been redirects, the original address shall be
used.
Subject:
Set to the string "X.400 Inter-Personal Notification" for a
receipt notification and to "X.400 Inter-Personal
Notification (failure)" for a non-receipt notification.
Message-Type:
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Set to "InterPersonal Notification"
References:
Set to IPMS.IPN.subject-ipm
Discarded-X400-IPMS-Extensions:
Used for any discarded IPN extensions.
The following EBNF is defined for the body of the Message. This
format is defined to ensure that all information from an
interpersonal notification is available to the end user in a
uniform manner.
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ipn-body-format = ipn-description <CRLF>
[ ipn-extra-information <CRLF> ]
[ ipn-content-return ]
ipn-description = ipn-receipt / ipn-non-receipt
ipn-receipt = "Your message to:" preferred-recipient <CRLF>
"was received at" receipt-time <CRLF> <CRLF>
"This notification was generated"
acknowledgement-mode <CRLF>
"The following extra information was given:" <CRLF>
ipn-suppl <CRLF>
ipn-non-receipt = "Your message to:"
preferred-recipient <CRLF>
ipn-reason
ipn-reason = ipn-discarded / ipn-auto-forwarded
ipn-discarded = "was discarded for the following reason:"
discard-reason <CRLF>
ipn-auto-forwarded = "was automatically forwarded." <CRLF>
[ "The following comment was made:"
auto-comment ]
ipn-extra-information =
"The following information types were converted:"
encoded-info
ipn-content-return = "The Original Message is not available"
/ "The Original Message follows:"
preferred-recipient = mailbox
receipt-time = date-time
auto-comment = printablestring
ipn-suppl = printablestring
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discard-reason = "Expired" / "Obsoleted" /
"User Subscription Terminated" / "IPM Deleted"
acknowledgement-mode = "Manually" / "Automatically"
The mappings for elements of the common fields of IPMS.IPN
(IPMS.CommonFields) onto this structure and the message header
are:
subject-ipm
Mapped to "References:"
ipn-originator
Mapped to "From:".
ipn-preferred-recipient
Mapped to EBNF.preferred-recipient
conversion-eits
Mapped to EBNF.encoded-info in EBNF.ipn-extra-information
The mappings for elements of IPMS.IPN.non-receipt-fields
(IPMS.NonReceiptFields) are:
non-receipt-reason
Used to select between EBNF.ipn-discarded and
EBNF.ipn-auto-forwarded
discard-reason
Mapped to EBNF.discard-reason
auto-forward-comment
Mapped to EBNF.auto-comment
returned-ipm
This applies only to non-receipt notifications.
EBNF.ipn-content-return shall always be omitted for receipt
notifications, and always be present in non-receipt
notifications. If present, the second option of
EBNF.ipn-content-return is chosen, and the message is
included. In this case, the message is formatted as
multipart/mixed, and the returned message included as
message/rfc822 after the text body part. Otherwise the first
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option is chosen.
The mappings for elements of IPMS.IPN.receipt-fields
(IPMS.ReceiptFields) are:
receipt-time
Mapped to EBNF.receipt-time
acknowledgement-mode
Mapped to EBNF.acknowledgement-mode
suppl-receipt-info
Mapped to EBNF.ipn-suppl
An example notification is:
From: Steve Kille <steve@cs.ucl.ac.uk>
To: Julian Onions <jpo@computer-science.nottingham.ac.uk>
Subject: X.400 Inter-personal Notification
Message-Type: InterPersonal Notification
References: <1229.614418325@UK.AC.NOTT.CS>
Date: Wed, 21 Jun 89 08:45:25 +0100
Your message to: Steve Kille <steve@cs.ucl.ac.uk>
was automatically forwarded.
The following comment was made:
Sent on to a random destination
The following information types were converted: g3fax
5.3.6. Mappings from the MTS Abstract Service
This section describes the MTS mappings for User Messages (IPM
and IPN). This mapping is defined by specifying the mapping of
MTS.MessageDeliveryEnvelope. The following extensions to RFC 822
are defined to support this mapping:
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mts-field = "X400-MTS-Identifier" ":" mts-msg-id
/ "X400-Originator" ":" mailbox
/ "X400-Recipients" ":" 1#mailbox
/ "Original-Encoded-Information-Types" ":"
encoded-info
/ "X400-Content-Type" ":" mts-content-type
/ "X400-Content-Identifier" ":" printablestring
/ "Priority" ":" priority
/ "Originator-Return-Address" ":" 1#mailbox
/ "DL-Expansion-History" ":" mailbox ";" date-time ";"
/ "Conversion" ":" prohibition
/ "Conversion-With-Loss" ":" prohibition
/ "Delivery-Date" ":" date-time
/ "Discarded-X400-MTS-Extensions" ":"
1#( object-identifier / labelled-integer )
prohibition = "Prohibited" / "Allowed"
mts-msg-id = "[" global-id ";" *text "]"
mts-content-type = "P2" / labelled-integer
/ object-identifier
priority = "normal" / "non-urgent" / "urgent"
The mappings for each element of MTS.MessageDeliveryEnvelope can
now be considered. Where the specified action does not result in
an extended element being mapped, the criticality associated with
this element shall be considered. If the element is marked as
critical for transfer or for delivery, the message shall be non
delivered by the gateway because a critical extension cannot be
correctly handled.
MTS.MessageDeliveryEnvelope.message-delivery-identifier
Mapped to the extended RFC 822 field "X400-MTS-Identifier:".
MTS.MessageDeliveryEnvelope.message-delivery-time
Discarded, as this time will be represented in an
appropriate trace element.
The mappings for elements of
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MTS.MessageDeliveryEnvelope.other-fields
(MTS.OtherMessageDeliveryFields) are:
content-type
Mapped to the extended RFC 822 field "X400-Content-Type:".
The string "P2" is retained for backwards compatibility with
RFC 987. This shall not be generated, and either the
EBNF.labelled-integer or EBNF.object-identifier encoding
used.
originator-name
Mapped to the SMTP originator, and to the extended RFC 822
field "X400-Originator:". This is described in
Section 4.6.2.
original-encoded-information-types
Mapped to the extended RFC 822 field
"Original-Encoded-Information-Types:".
priority
Mapped to the extended RFC 822 field "Priority:".
delivery-flags
If the conversion-prohibited bit is set, add an extended RFC
822 field "Conversion:".
this-recipient-name and other-recipient-names
The handling of these elements is described in
Section 4.6.2.
originally-intended-recipient-name
The handling of this element is described in Section 4.6.2.
converted-encoded-information-types
Discarded. This information will be mapped in the trace.
message-submission-time
Mapped to Date:.
content-identifier
Mapped to the extended RFC 822 field
"X400-Content-Identifier:". In RFC 1327, this was
"Content-Identifier:". This has been changed to avoid
confusion with MIME defined fields. Gateways which reverse
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map, may support the old field.
If any extensions
(MTS.MessageDeliveryEnvelope.other-fields.extensions) are
present, and they are marked as critical for transfer or
delivery, then the message shall be rejected. The extensions
(MTS.MessageDeliveryEnvelope.other-fields.extensions) are mapped
as follows.
conversion-with-loss-prohibited
If set to
MTS.ConversionWithLossProhibited.conversion-with-loss-prohibited,
then add the extended RFC 822 field "Conversion-With-Loss:".
requested-delivery-method
Mapped to a comment, as described in Section 4.6.2.2.
originator-return-address
Mapped to the extended RFC 822 field
"Originator-Return-Address:".
physical-forwarding-address-request
physical-delivery-modes
registered-mail-type
recipient-number-for-advice
physical-rendition-attributes
physical-delivery-report-request
physical-forwarding-prohibited
These elements are only appropriate for physical delivery.
They are represented as comments in the "X400-Recipients:"
field, as described in Section 4.6.2.2.
originator-certificate
message-token
content-confidentiality-algorithm-identifier
content-integrity-check
message-origin-authentication-check
message-security-label
proof-of-delivery-request
These elements imply use of security services not available
in the RFC 822 environment. If they are marked as critical
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for transfer or delivery, then the message shall be
rejected. Otherwise they are discarded.
redirection-history
This is described in Section 4.6.2.
dl-expansion-history
Each element is mapped to an extended RFC 822 field
"DL-Expansion-History:". These fileds shall be ordered in
the message header, so that the most recent expansion comes
first (same order as trace).
If any MTS (or MTA) Extensions not specified in X.400 are
present, and they are marked as critical for transfer or
delivery, then the message shall be rejected. If they are not so
marked, they can safely be discarded. The list of discarded
fields shall be indicated in the extended header
"Discarded-X400-MTS-Extensions:".
5.3.7. Mappings from the MTA Abstract Service
There are some mappings at the MTA Abstract Service level which
are done for IPM and IPN. These can be derived from
MTA.MessageTransferEnvelope. The reasons for the mappings at
this level, and the violation of layering are:
- Allowing for multiple recipients to share a single RFC 822
message
- Making the X.400 trace information available on the RFC 822
side
- Making any information on deferred delivery available
The SMTP recipients are calculated from the full list of X.400
recipients. This is all of the members of
MTA.MessageTransferEnvelope.per-recipient-fields being passed
through the gateway, where the responsibility bit is set. In
some cases, a different RFC 822 message would be calculated for
each recipient, due to differing service requests for each
recipient. As discussed in 4.6.2.2, this specification allows
either for multiple messages to be generated, or for the per-
recipient information to be discarded.
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The following EBNF is defined for extended RFC 822 headers:
mta-field = "X400-Received" ":" x400-trace
/ "Deferred-Delivery" ":" date-time
/ "Latest-Delivery-Time" ":" date-time
x400-trace = "by" md-and-mta ";"
[ "deferred until" date-time ";" ]
[ "converted" "(" encoded-info ")" ";" ]
[ "attempted" md-or-mta ";" ]
action-list
";" arrival-time
md-and-mta = [ "mta" mta "in" ] global-id
mta = word
arrival-time = date-time
md-or-mta = "MD" global-id
/ "MTA" mta
Action-list = 1#action
action = "Redirected"
/ "Expanded"
/ "Relayed"
/ "Rerouted"
Note the EBNF.mta is encoded as 822.word. If the character
set does not allow encoding as 822.atom, the 822.quoted-string
encoding is used.
If MTA.PerMessageTransferFields.deferred-delivery-time is
present, it is used to generate a Deferred-Delivery: field.
X.400 does not make this information available at the MTS level
on delivery, because it requires that this service is provided by
the first MTA. In the event that the first MTA does not provide
this service, the function may optionally be implemented by the
gateway: that is, the gateway may hold the message until the time
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specified in the protocol element. Thus, the value of this
element will usually be in the past. For this reason, the
extended RFC 822 field is primarily for information.
If MTA.PerMessageTransferFields.extensions.dl-expansion-
prohibited is present and set to dl-expansion-probited, the
gateway may reject that message on the basis that it is unable to
control distribution list expansion beyond the gateway. The
service relating to this is described in Section 2.3.1.2. This
approach was not specified in RFC 1327. If it is found to be
useful, it may be made mandatory in future versions of MIXER.
If MTA.PerMessageTransferFields.extensions.recipient-
reassignment-prohibited is present and set to
recipeint-reassignment-probited, the gateway may reject that
message on the basis that it is unable to control distribution
list expansion beyond the gateway. The service relating to this
is described in Section 2.3.1.2. This approach was not
specified in RFC 1327. If it is found to be useful, it may be
made mandatory in future versions of MIXER.
Merge MTA.PerMessageTransferFields.trace-information, and
MTA.PerMessageTransferFields.internal-trace-information to
produce a single ordered trace list. If Internal trace from
other management domains has not been stripped, this may require
complex interleaving. Where an element of internal trace and
external trace are identical, except for the MTA in the internal
trace, only the internal trace element shall be presented. Use
this to generate a sequence of "X400-Received:" fields. The only
difference between external trace and internal trace will be the
extra MTA information in internal trace elements.
When generating an RFC 822 message all trace fields (X400-
Received and Received) shall be at the beginning of the header,
before any other fields. Trace shall be in chronological order,
with the most recent element at the front of the message. This
ordering is determined from the order of the fields, not from
timestamps in the trace, as there is no guarantee of clock
synchronisation. A simple example trace (external) is:
X400-Received: by /PRMD=UK.AC/ADMD=Gold 400/C=GB/ ; Relayed ;
Tue, 20 Jun 89 19:25:11 +0100
A more complex example (internal):
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MIXER DRAFT Version 2.6
X400-Received: by mta "UK.AC.UCL.CS" in /PRMD=UK.AC/ADMD=Gold 400/C=GB/ ;
deferred until Tue, 20 Jun 89 14:24:22 +0100 ;
converted (undefined, g3fax) ; attempted MD /ADMD=Foo/C=GB/ ;
Relayed, Expanded, Redirected ; Tue, 20 Jun 89 19:25:11 +0100
The gateway itself shall add a single line of trace
information, indicating MIXER conversion by use of a comment.
For example:
Received: from isode.com by isode.com
(MIXER Conversion following RFC 1327);
Thu, 2 Jan 1997 14:46:03 +0000
If SMTP is being used, Appendix A shall also be followed,
which includes optional mappings to extension parameters.
5.3.8. Mappings from Report Delivery
Delivery reports are mapped at the MTS service level. This means
that only reports destined for the MTS user will be mapped. Some
additional services are also taken from the MTA service. X.400
Delivery Reports are Mapped onto Delivery Status Notifications,
as defined by NOTARY [28].
5.3.8.1. MTS Mappings
A Delivery Report service will be represented as
MTS.ReportDeliveryEnvelope, which comprises of per-report-fields
(MTS.PerReportDeliveryFields) and per-recipient-fields.
The enclosing message is a MIME message of content type
multipart/report, with report-type=delivery-status, which is
generated with the following fields:
From:
An administrator at the gateway system.
To: A mapping of the
MTA.ReportTransferEnvelope.report-destination-name. This is
also the SMTP recipient.
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Message-Type:
Set to "Delivery Report". This is strictly redundant, but
retained for backwards compatibility with RFC 1327.
Subject:
The EBNF for the subject line is:
subject-line = "Delivery-Report" "(" status ")"
[ "for" destination ]
status = "success" / "failure" / "success and failures"
destination = mailbox / "MTA" word
The subject is intended to give a clear indication as to the
nature of the message, and summarise its contents. EBNF.status is
set according to whether the recipients reported on are all
successes, all failures, or a mixture. It is common for a report
to reference a single recipient, in which case a subject line
giving using all of the options of EBNF.status can be used. This
gives useful information to the recipient. Where information
varies between reported recpients, the options cannot be used.
The EBNF.destination is used to indicate the addresses in the
reports. If the report is for a single address, EBNF.mailbox is
used to give the RFC 822 representation of the address. If all
of the reported recpients reference the same MTA this is included
in EBNF.word. The MTA is determined from the delivery report's
trace.
The format of the body of the message follows the NOTARY
delivery status notification format, and is defined to ensure
that all information is conveyed to the RFC 822 user in a
consistent manner. The format is structured as if it was a
message coming from the gateway, with three body parts. The first
body part is ASCII text structured as follows:
1. A few lines giving keywords to indicate the original
message.
2. A human summary of the status of each recipient being
reported on.
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The second (mandatory) body part is the NOTARY delivery
status notification, which contains detailed information
extracted from the report. This information may be critical to
diagnosing an obscure problem.
The third (optional) body part contains the returned message
(return of content). This structure is useful to the RFC 822
recipient, as it enables the original message to be extracted.
For negative reports it shall be included if the original message
is available. For positive reports headers from the message
shall be included if the original message is available.
The first body part containing the user oriented description
is of type text/plain. The format of this body part is defined
below as EBNF.dr-user-info.
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dr-user-info = dr-summary <CRLF>
dr-recipients <CRLF>
dr-content-return
dr-content-return = "The Original Message is not available"
/ "The Original Message follows:"
dr-summary = "This report relates to your message:" <CRLF>
content-correlator <CRLF> <CRLF>
"of" date-time <CRLF> <CRLF>
dr-recipients = *(dr-recipient <CRLF> <CRLF>)
dr-recipient = dr-recip-success / dr-recip-failure
dr-recip-success =
"Your message was successfully delivered to:"
mailbox "at" date-time
dr-recip-failure = "Your message was not delivered to:"
mailbox <CRLF>
"for the following reason:" *word
report-point = [ "mta" mta-name "in" ] global-id
content-correlator = *word
mta-name = word
EBNF.dr-summary
The EBNF.content-correlator is taken from the content
correlator (or content identifier if there is no content
correlator) and the EBNF.date-time from the trace, as
described in Section 5.3.8.3. LWSP may be added to improve
the layout of the body part.
EBNF.dr-recipients
There is an element for each recipient in the delivery
report. In each case, EBNF.mailbox is taken from the RFC
822 form of the originally specified recipient, which is
taken from the originally specified recipient element if
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present or from the actual recipient. When reporting
success, the message delivery time is used to derive
EBNF.date-time. When reporting failure, the information
includes a human readable interpretation of the X.400
diagnostic and reason codes, and the supplementary
information.
EBNF.dr-content-return
This is set according to whether or not the content is being
returned.
The EBNF of this body part is designed for english-speaking
users. The language of the strings in the EBNF may be altered.
The EBNF used in the delivery status notification is:
dr-per-message-fields =
/ "X400-Conversion-Date" ":" date-time
/ "X400-Subject-Submision-Identifier" ":"
mts-msg-id
/ "X400-Content-Identifier" ":" printablestring
/ "X400-Content-Type" ":" mts-content-type
/ "X400-Original-Encoded-Information-Types" ":"
encoded-info
/ "X400-Originator-and-DL-Expansion-History" ":"
mailbox ";" date-time ";"
/ "X400-Reporting-DL-Name" ":" mailbox
/ "X400-Content-Correlator" ":" content-correlator
/ "X400-Recipient-Info" ":" recipient-info
/ "X400-Subject-Intermediate-Trace-Information" ":"
x400-trace
/ dr-extensions
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dr-per-recipient-fields =
/ "X400-Redirect-Recipient" ":" "x400" ";" std-or
/ "X400-Mapped-Redirect-Recipient" ":" "rfc822" ";" mailbox
/ "X400-Converted-EITs" ":" encoded-info ";"
/ "X400-Delivery-Time" ":" date-time
/ "X400-Type-of-MTS-User" ":" labelled-integer
/ "X400-Last-Trace" ":" [ encoded-info ] date-time
/ "X400-Supplementary-Info" ":"
<"> printablestring <"> ";"
/ "X400-Redirection-History" ":" redirect-history-item
/ "X400-Physical-Forwarding-Address" ":" mailbox
/ "X400-Originally-Specified-Recipient-Number" ":"
integer
/ dr-extensions
dr-extensions = "X400-Discarded-DR-Extensions" ":"
1# (object-identifier / labelled-integer)
dr-diagnostic = "Reason" labelled-integer-2
[ ";" "Diagnostic" labelled-integer-2 ]
A body part of type delivery status, as defined by NOTARY, is
generated. MIXER extends this delivery status notification (DSN)
specification, by defining additional per message fields in
EBNF.dr-per-message-fields and additional per recipient fields in
EBNF.dr-per-recipient-fields. These are used as extensions to
DSN.per-message-fields and DSN.per-recipient-fields. MIXER also
defines a new NOTARY address type "x400", with encoding of
EBNF.std-or. A directory name may be inluded as an RFC 822
comment.
The following DSN.per-message-fields are always generated:
DSN.reporting-mta-field
The DSN.mta-name-type is set to "x400", and this string is
reserved by MIXER. The DSN.mta-name has its syntax
specified by EBNF.report-point, with the information derived
from the first element of the DR's trace.
DSN.arrival-date-field
This is derived from the date of the
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MTA.PerRecipientReportTransferFields.last-trace-info.arrival-time
of the first recipient in the report.
The following two EBNF.per-message-fields are generated by
the MIXER gateway:
DSN.dsn-gateway-field
The type is set to "dns" and the domain set to the local
domain of the gateway.
X400-Conversion-Date:
The EBNF.date-time is set to the time of the MIXER
conversion.
The elements of MTS.ReportDeliveryEnvelope.per-report-fields
are mapped as follows onto the DSN per message fields as follows:
subject-submission-identifier
Mapped to DSN.original-envelope-id-field. The encoding of
this MTS Identifier follows the format EBNF.mts-msg-id.
content-identifier
Mapped to X400-Content-Identifier:
content-type
Mapped to X400-Content-Type:
original-encoded-information-types
Mapped to X400-Encoded-Info:
The extensions from
MTS.ReportDeliveryEnvelope.per-report-fields.extensions are
mapped as follows:
originator-and-DL-expansion-history
Each element is mapped to an
"X400-Originator-and-DL-Expansion-History:" They shall be
ordered so that the most recent expansion comes first in the
header (same order as trace).
reporting-DL-name
Mapped to X400-Reporting-DL-Name:
content-correlator
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If the content correlator starts with the string
"SMTP/NOTARY ENVID: ", then the remainder of the content
correlator is mapped to the DSN original-envelope-id field.
If this is not the case, the content correlator is mapped to
X400-Content-Correlator:, provided that the encoding is
IA5String (this will always be the case).
message-security-label
reporting-MTA-certificate
report-origin-authentication-check
These security parameters will not be present unless there
is an error in a remote MTA. If they are present, they
shall be discarded in preference to discarding the whole
report. They shall be listed in the X400-Discarded-DR-
Extensions: field.
If there are any other DR extensions, they shall also be
discarded and listed in the X400-Discarded-DR-Extensions: field.
For each element of
MTS.ReportDeliveryEnvelope.per-recipient-fields, a set of
DSN.per-recipient-fields is generated. The fields are filled in
as follows:
actual-recipient-name
If originally-intended-recipient-name is not present,
generate a DSN.original-recipient-field fields, with
DSN.address-type of "rfc822", and with an RFC 822 mailbox
generated from the address encoded as specified by NOTARY.
Also generate a DSN.final-recipient-field field, which holds
the X.400 representation of the same address. If the
directory name is present, it shall be added as a trailing
comment in the X.400 form.
If originally-intended-recipient-name is present, generate
an "X400-Mapped-Redirect-Recipient:" field, with
DSN.address-type of "rfc822", and with an RFC 822 mailbox
generated from the address encoded as specified by NOTARY.
Also generate an "X400-Redirect-Recipient:" field, which
holds the X.400 representation of the same address. If the
directory name is present, it shall be added as a trailing
comment in the X.400 form.
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report
If it is MTS.Report.delivery, then set DSN.action-field to
"delivered", and set "X400-Delivery-Time:" and
"X400-Type-of-MTS-User:" from the information in the report.
DSN.status field is set to "2.0.0".
If it is MTS.Report.non-delivery, then set DSN.action-field
to "failed". DSN.diagnostic-code-field is encoded
according to the syntax EBNF.dr-diagnostic, with the
labelled integers set from the reason and diagnostic codes.
DSN.status-field is derived from the reason and diagnostic
codes, as described below.
converted-encoded-information-types
Set X400-Converted-EITs:
originally-intended-recipient
Generate a DSN.final-recipient-field field, with
DSN.address-type of "rfc822", and with an RFC 822 mailbox
generated from the address encoded as specified by NOTARY.
Also generate a DSN.original-recipient-field field, which
holds the X.400 representation of the same address. If the
directory name is present, it shall be added as a trailing
comment in the X.400 form.
supplementary-info
Set X400-Supplementary-Info:
redirection-history
Generate an "X400-Redirection-History:" field for each
redirect history element. The fields are ordered with the
earliest redirect first.
physical-forwarding-address
Set X400-Physical-Forwarding-Address as a mailbox, with
directory name in comment if present.
recipient-certificate
Discard
proof-of-delivery
Discard
Any unknown extensions shall be discarded, irrespective of
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criticality. All discarded extensions shall be included in a
"X400-Discarded-DR-Extensions:" field.
The number from the
MTA.PerRecipientReportTransferFields.originally-specified-recipient-number
shall be mapped to "X400-Originally-Specified-Recipient-Number:",
in order to facilitate reverse mapping of delivery reports.
The original message shall be included in the delivery
status notification if it is available. The original message will
usually be available at the gateway, as discussed in Section 5.2.
If the original message is available, but is not a legal message
format, a dump of the ASN.1 may be included, encoded as
application/octet-string. This is recommended, but not required.
Where the original message is included, it shall be encoded
according to the MIME specifications as content type
message/rfc822.
5.3.8.2. Status Code Mappings
This section defines the mappings from X.400 diagnostic and
status codes to the NOTARY Status field.
C/D X400 meaning DSN code Means
0/Any Transfer failure (may be temporary) 4.4.0 Other net/route
1/Any Unable to transfer 5.0.0 Other, unknown
2/Any Conversion not performed 5.6.3 Conv not supported
3/Any Physical rendition not performed 5.6.0 Other media error
4/Any Physical delivery not performed 5.1.0 Other address status
5/Any Restricted delivery 5.7.1
6/Any Directory operation unsuccessful 5.4.3 Routing server failure
7/Any Deferred delivery not performed 5.3.3 Not capable
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1/0 Unrecognized OR name 5.1.1
1/1 Ambiguous OR name 5.1.4
1/2 MTS congestion 4.3.1
1/3 Loop detected 5.4.6
1/4 Recipient unavailable 4.2.1
1/5 Delivery time expired 4.4.7
1/6 Encoded information types unsupported 5.6.1 Media unsupp.
1/7 Content too long 5.2.3
2/8 Conversion impractical 5.6.3
2/9 Conversion prohibited 5.6.3
1/10 Implicit conversion not subscribed 5.6.3
1/11 Invalid arguments 5.5.2
1/12 Content syntax error 5.5.2
1/13 Size constraint violation 5.5.2
1/14 Protocol violation 5.5.0
1/15 Content type not supported 5.6.1 Media unsupp.
1/16 Too many recipients 5.5.3
1/17 No bilateral agreement 5.4.4
1/18 Unsupported critical function 5.3.3 System not capable
2/19 Conversion with loss prohibited 5.6.2
2/20 Line too long 5.6.0
2/21 Page split 5.6.0
2/22 Pictorial symbol loss 5.6.2
2/23 Punctuation symbol loss 5.6.2
2/24 Alphabetic character loss 5.6.2
2/25 Multiple information loss 5.6.2
1/26 Recipient reassignment prohibited 5.4.0 Undefined net/route
1/27 Redirection loop detected 5.4.6
1/28 DL expansion prohibited 5.7.2
1/29 No DL submit permission 5.7.1 Delivery not authorized
1/30 DL expansion failure 4.2.4
4/31 Physical rendition attrs not supported 5.6.0 Undefined media error
4/32-45 Various physical mail stuff 5.1.0 Other address status
1/43 New address unknown 5.1.6 Destination mbox moved
1/46 Secure messaging error 5.7.0 Other security status
2/47 Unable to downgrade 5.3.3 System not capable
0/48 Unable to complete transfer 5.3.4 Message too big
0/49 Transfer attempts limit reached 4.4.7 Delivery time expired
5.3.8.3. MTA Mappings
The single SMTP recipient is constructed from
Kille [page 128]
RFC 1327bis
MIXER DRAFT Version 2.6
MTA.ReportTransferEnvelope.report-destination-name, using the
mappings of Chapter 4. Unlike with a user message, this
information is not available at the MTS level.
The following additional mappings are made, which results in
fields in the outer header of the DSN.
MTA.ReportTransferEnvelope.report-destination-name
This is used to generate the To: field.
MTA.ReportTransferEnvelope.identifier
Mapped to the extended RFC 822 field "X400-MTS-Identifier:".
It may also be used to derive a "Message-Id:" field.
MTA.ReportTransferEnvelope.trace-information
and
MTA.ReportTransferEnvelope.internal-trace-information
Mapped onto the extended RFC 822 field "X400-Received:", as
described in Section 5.3.7. Date: is generated from the
first element of trace.
The following additional mappings are made, which result in per
message fields in the DSN body part:
MTA.PerRecipientReportTransferFields.last-trace-information
Mapped to X400-Last-Trace:".
MTA.PerReportTransferFields.subject-intermediate-trace-
information Mapped to
"X400-Subject-Intermediate-Trace-Information:". These fields
are ordered so that the most recent trace element comes
first.
5.3.8.4. Example Delivery Reports
This section contains sample delivery reports. These are the
same examples used in RFC 1327, and so they also illustrate the
changes between RFC 1327 and this document. Example Delivery
Report 1:
Kille [page 129]
RFC 1327bis
MIXER DRAFT Version 2.6
Received: from cs.ucl.ac.uk by bells.cs.ucl.ac.uk
via Delivery Reports Channel id <27699-0@bells.cs.ucl.ac.uk>;
Thu, 7 Feb 1991 15:48:39 +0000
From: UCL-CS MTA <postmaster@cs.ucl.ac.uk>
To: S.Kille@cs.ucl.ac.uk
Subject: Delivery Report (failure) for H.Hildegard@bbn.com
Message-Type: Delivery Report
Date: Thu, 7 Feb 1991 15:48:39 +0000
Message-ID: <"bells.cs.u.694:07.01.91.15.48.34"@cs.ucl.ac.uk>
X400-Content-Identifier: Greetings.
MIME-Version: 1.0
Content-Type: multipart/report; report-type=delivery-status;
boundary=boundary-1
--boundary-1
This report relates to your message:
Greetings.
of Thu, 7 Feb 1991 15:48:20 +0000
Your message was not delivered to
H.Hildegard@bbn.com for the following reason:
Bad Address
MTA 'bbn.com' gives error message (USER) Unknown user name in
"H.Hildegard@bbn.com"
The Original Message follows:
--boundary-1
content-type: message/delivery-status
Kille [page 130]
RFC 1327bis
MIXER DRAFT Version 2.6
Reporting-MTA: x400; bells.cs.ucl.ac.uk in /PRMD=uk.ac/ADMD=gold 400/C=gb/
Arrival-Date: Thu, 7 Feb 1991 15:48:34 +0000
DSN-Gateway: dns; bells.cs.ucl.ac.uk
X400-Conversion-Date: Thu, 7 Feb 1991 15:48:40 +0000
Original-Envelope-Id:
[/PRMD=uk.ac/ADMD=gold 400/C=gb/;<1803.665941698@UK.AC.UCL.CS>]
X400-Content-Identifier: Greetings.
X400-Subject-Intermediate-Trace-Information: /PRMD=uk.ac/ADMD=gold 400/C=gb/;
arrival Thu, 7 Feb 1991 15:48:20 +0000 action Relayed
X400-Subject-Intermediate-Trace-Information: /PRMD=uk.ac/ADMD=gold 400/C=gb/;
arrival Thu, 7 Feb 1991 15:48:18 +0000 action Relayed
Original-Recipient: rfc822; H.Hildegard@bbn.com
Final-Recipient: x400;
/RFC-822=H.Hildegard(a)bbn.com/OU=cs/O=ucl/PRMD=uk.ac/ADMD=gold 400/C=gb/;
Action: failure
Status: 5.1.1
Diagnostic-Code: x400; Reason 1 (Unable-To-Transfer);
Diagnostic 0 (Unrecognised-ORName)
X400-Last-Trace: (ia5) Thu, 7 Feb 1991 15:48:18 +0000;
X400-Originally-Specified-Recipient-Number: 1
X400-Supplementary-Info: "MTA 'bbn.com' gives error message (USER)
Unknown user name in "H.Hildegard@bbn.com"";
Kille [page 131]
RFC 1327bis
MIXER DRAFT Version 2.6
--boundary-1
Content-Type: message/rfc822
Received: from glenlivet.cs.ucl.ac.uk by bells.cs.ucl.ac.uk
with SMTP inbound id <27689-0@bells.cs.ucl.ac.uk>;
Thu, 7 Feb 1991 15:48:21 +0000
To: H.Hildegard@bbn.com
Subject: Greetings.
Phone: +44-71-380-7294
Date: Thu, 07 Feb 91 15:48:18 +0000
Message-ID: <1803.665941698@UK.AC.UCL.CS>
From: Steve Kille <S.Kille@cs.ucl.ac.uk>
Steve
--boundary-1--
Kille [page 132]
RFC 1327bis
MIXER DRAFT Version 2.6
Example Delivery Report 2:
Received: from cs.ucl.ac.uk by bells.cs.ucl.ac.uk
via Delivery Reports Channel id <27718-0@bells.cs.ucl.ac.uk>;
Thu, 7 Feb 1991 15:49:11 +0000
X400-Received: by mta "bells.cs.ucl.ac.uk" in /PRMD=uk.ac/ADMD=gold 400/C=gb/;
Relayed; Thu, 7 Feb 1991 15:49:08 +0000
X400-Received: by /PRMD=DGC/ADMD=GOLD 400/C=GB/; Relayed;
Thu, 7 Feb 1991 15:48:40 +0000
From: UCL-CS MTA <postmaster@cs.ucl.ac.uk>
To: S.Kille@cs.ucl.ac.uk
Subject: Delivery Report (failure) for
j.nosuchuser@dle.cambridge.DGC.gold-400.gb
Message-Type: Delivery Report
Date: Thu, 7 Feb 1991 15:46:11 +0000
Message-ID: <"DLE/910207154840Z/000"@cs.ucl.ac.uk>
X400-Content-Identifier: A useful mess...
MIME-Version: 1.0
Content-Type: multipart/report; report-type=delivery-status;
boundary=boundary-1
--boundary-1
This report relates to your message:
A useful mess...
of Thu, 7 Feb 1991 15:43:20 +0000
Your message was not delivered to
j.nosuchuser@dle.cambridge.DGC.gold-400.gb
for the following reason:
Bad Address
DG 21187: (CEO POA) Unknown addressee.
The Original Message is not available
Kille [page 133]
RFC 1327bis
MIXER DRAFT Version 2.6
--boundary-1
content-type: message/delivery-status
Reporting-MTA: x400; /PRMD=DGC/ADMD=GOLD 400/C=GB/
Arrival-Date: Thu, 7 Feb 1991 15:48:40 +0000
DSN-Gateway: dns; bells.cs.ucl.ac.uk
X400-Conversion-Date: Thu, 7 Feb 1991 15:49:12 +0000
Original-Envelope-Id:
[/PRMD=uk.ac/ADMD=gold 400/C=gb/;<1796.665941626@UK.AC.UCL.CS>]
X400-Content-Identifier: A useful mess...
Original-Recipient: rfc822; j.nosuchuser@dle.cambridge.DGC.gold-400.gb
Final-Recipient: x400;
/I=j/S=nosuchuser/OU=dle/O=cambridge/PRMD=DGC/ADMD=GOLD 400/C=GB/
Action: failure
Status: 5.1.1
Diagnostic-Code: x400; Reason 1 (Unable-To-Transfer);
Diagnostic 0 (Unrecognised-ORName)
X400-Supplementary-Info: "DG 21187: (CEO POA) Unknown addressee."
X400-Originally-Specified-Recipient-Number: 1
--boundary-1--
5.3.9. Probe
This is an MTS internal issue. Any probe shall be serviced by
the gateway, as there is no equivalent RFC 822 functionality.
The value of the reply is dependent on whether the gateway could
service an MTS Message with the values specified in the probe.
The reply shall make use of MTS.SupplementaryInformation to
indicate that the probe was serviced by the gateway.
Kille [page 134]
RFC 1327bis
MIXER DRAFT Version 2.6
Appendix A - Mappings Specific to SMTP
This Appendix is specific to the Simple Mail Transfer Protocol
(RFC 821). It describes specific changes in the context of this
protocol. When MIXER is used with SMTP, conformance to this
appendix is mandatory.
1. Probes
When servicing a probe, as described in section 5.3.9, use may be
made of the SMTP VRFY command to increase the accuracy of
information contained in the delivery report.
2. Long Lines
SMTP is a text oriented protocol, and is required to support a
line length of at least 1000 characters. Some implementations
do not support line lengths greater than 1000 characters. This
can cause problems. Where body parts have long lines, it is
recommended to use a MIME encoding that folds lines (quoted
printable).
3. SMTP Extensions
There are several RFCs that specify extensions to SMTP. Most of
these are not relevant to MIXER. The NOTARY work to support
delivery report defines extensions which are relevant [29]. Use
of these extensions by a MIXER gateway is optional. If these
extensions are used, they shall be used in the manner described
below.
3.1. SMTP Extension mapping to X.400
Mappings are defined for the following extensions:
NOTIFY
This is used to set the report and non-delivery bits of
MTA.PerRecipientMessageTransferFields.per-recipient-indicators.
If the value is NEVER, both bits are zero. If SUCCESS is
present, the report bit is set. Otherwise, the non-
delivery-report bit is set. If the gateway uses the NOTIFY
command, it shall perform this mapping in all cases.
Kille [page 135]
RFC 1327bis
MIXER DRAFT Version 2.6
ORCPT
If the address type of the original recipient is "x400" or
"rfc822", this may be used at the MTS level, to generate an
element of redirection history, with the redirection date
being the date of conversion and the reason set to "alias".
ENVID
If present, this may be used to generate a content
correlator. This is used rather than the MTS Identifier,
as the ENVID is unique for the UA only and is likely to be
too large to map to an MTS identifier. The content
correlator is encoded as an IA5 String containing the ENVID
and prefixed by the string:
"SMTP/NOTARY ENVID: "
If the ENVID starts with the string "X400-MTS-Identifier: ",
then this ENVID was generated from an X.400 MTS Identifier.
The reverse mapping defined in Section 3.2 of Appendix A
shall not be used, as this may cause problems in certain
situations (e.g., where the message was expanded by an
Internet mailing list).
3.2. X.400 Mapping to SMTP Extensions
The following extensions may be used as a part of the MIXER
mapping:
NOTIFY
The originator-report and originator-non-delivery-report
bits of
MTA.PerRecipientMessageTransferFields.per-recipient-indicators
determine how this is used. If both bits are zero, the
parameter is NEVER. If the report bit is set, SUCCESS is
used. Otherwise, FAILURE is used. If this is done, the
gateway shall not generate a delivery report for this
recipient, unless this is needed in the case where the
originating MTA service report requirements differ from the
user requirements. Additional originating MTA
requrirements are satisfied by the gateway.
ORCPT
If the
MTS.perRecipientDeliveryFields.originally-intended-recipient-name
Kille [page 136]
RFC 1327bis
MIXER DRAFT Version 2.6
is present, the ORCPT command may be used to carry this
value, using the "x400" syntax.
ENVID
This may be generated, with the value taken from the
MTS.MessageDeliveryEnvelope.message-delivery-identifer. If
this is done, it shall be encoded as EBNF.mts-msg-id,
preceded by the string "X400-MTS-Identifier: ".
RET
If
MTA.PerMessageTransferFields.per-message-indicators.content-return-request
is set to FALSE, the parameter RET may be set to HDRS, to
specify return of headers only.
Kille [page 137]
RFC 1327bis
MIXER DRAFT Version 2.6
Appendix B - Mapping with X.400(1984)
This appendix defines modifications to the mapping for use with
X.400(1984).
The X.400(1984) protocols are a proper subset of
X.400(1988). When mapping from X.400(1984) to RFC 822, no
changes to this specification are needed.
When mapping from RFC 822 to X.400(1984), no use can be made
of 1988 specific features. No use of such features is made at
the MTS level. The heading extension feature is used at the IPMS
level, and this shall be replaced by the RFC 987 approach. All
header information which would usually be mapped into the
rfc-822-heading-list extension is mapped into a single IA5 body
part, which is the first body part in the message. This body
part will start with the string "RFC-822-Headers:" as the first
line. The headers then follow this line. This specification
requires correct reverse mapping of this format, either from 1988
or 1984. RFC 822 extended headers which could be mapped into
X.400(1988) elements, are also mapped to the body part.
In an environment where RFC 822 is of major importance, it
may be desirable for downgrading to consider the case where the
message was originated in an RFC 822 system, and mapped according
to this specification. The rfc-822-heading-list extension may be
mapped according to this appendix.
When parsing std-or, the following restrictions shall be
observed:
- Only the 84/88 attributes identified in the table in
Section 4.2 are present.
- No teletex encoding is allowed.
If an address violates this, it shall be treated as an RFC 822
address, which will usually lead to encoding as a DDA "RFC-822".
It is possible that attributes of zero length may be present
in an OR Address. This is not legal in 1988, except for ADMD
where the case is explicitly described in Section 4.3.5.
Attributes of zero length are deprecated (the attribute shall be
Kille [page 138]
RFC 1327bis
MIXER DRAFT Version 2.6
omitted), and will therefore be unusual. However, some systems
generate them and rely on them. Therefore, any null attribute
shall be enoded using the std-or encoding (e.g., /O=/).
If a non-Teletex Common Name (CN) is present, it shall be
mapped onto a Domain Defined Attribute "Common". This is in line
with RFC 1328 on X.400 1988 to 1984 downgrading [22].
This specification defines a mapping of the Internet message
framework to X.400. Body part mappings are defined in RFC
1494bis [6], which relies on X.400(88) features. Downgrading to
X.400(84) for body parts is defined in RFC 1496 (HARPOON), which
shall be followed in the context of this appendix [5].
Kille [page 139]
RFC 1327bis
MIXER DRAFT Version 2.6
Appendix C - RFC 822 Extensions for X.400 access
This appendix defines a number of optional mappings which may be
provided to give access from RFC 822 to a number of X.400
services. These mappings are beyond the basic scope of this
specification. There has been a definite demand to use extended
RFC 822 as a mechanism to access X.400, and these extensions
provide access to certain features. If this functionality is
provided, this appendix shall be followed. The following
headings are defined:
extended-heading =
"Prevent-NonDelivery-Report" ":"
/ "Generate-Delivery-Report" ":"
/ "Alternate-Recipient" ":" prohibition
/ "Disclose-Recipients" ":" prohibition
/ "X400-Content-Return" ":" prohibition
Prevent-NonDelivery-Report and Generate-Delivery-Report allow
setting of
MTS.PerRecipientSubmissionFields.originator-report-request. The
setting will be the same for all recipients.
Alternate-Recipient, Disclose-Recipients, and X400-Content-
Return allow for override of the default settings for
MTS.PerMessageIndicators.
Use of NOTARY mechanisms is a preferred meachanism for
controlling these parameters.
Kille [page 140]
RFC 1327bis
MIXER DRAFT Version 2.6
Appendix D - Object Identifier Assignment
The following Object Identifiers shall be used.
internet ::= OBJECT IDENTIFIER { iso org(3) dod(6) 1 } -- from RFC 1155
mail OBJECT IDENTIFIER ::= { internet 7 } -- IANA assigned
mixer OBJECT IDENTIFIER ::= { mail mixer(1) } -- inherited from RFC 1495
mixer-core OBJECT IDENTIFIER ::= { mixer core(3) }
id-rfc-822-field-list OBJECT IDENTIFIER ::= {mixer-core 2}
id-dsn-header-list OBJECT IDENTIFIER ::= {mixer-core 3}
id-dsn-field-list OBJECT IDENTIFIER ::= {mixer-core 4}
eit-mixer OBJECT IDENTIFIER ::= {mixer-core 5}
-- the MIXER pseudo-EIT
This object identifier for id-rfc-822-field-list is different to
the one assigned in RFC 1327, which was erroneous.
Kille [page 141]
RFC 1327bis
MIXER DRAFT Version 2.6
Appendix E - BNF Summary
boolean = "TRUE" / "FALSE"
numericstring = *(DIGIT / " ")
printablestring = *( ps-char )
ps-restricted-char = 1DIGIT / 1ALPHA / " " / "'" / "+"
/ "," / "-" / "." / "/" / ":" / "=" / "?"
ps-delim = "(" / ")"
ps-char = ps-delim / ps-restricted-char
ps-encoded = *( ps-restricted-char / ps-encoded-char )
ps-encoded-char = "(a)" ; (@)
/ "(p)" ; (%)
/ "(b)" ; (!)
/ "(q)" ; (")
/ "(u)" ; (_)
/ "(l)" ; "("
/ "(r)" ; ")"
/ "(" 3DIGIT ")"
teletex-string = *( ps-char / t61-encoded )
t61-encoded = "{" 1* t61-encoded-char "}"
t61-encoded-char = 3DIGIT
teletex-and-or-ps = [ printablestring ] [ "*" teletex-string ]
labelled-integer ::= [ key-string ] "(" numericstring ")"
labelled-integer-2 ::= [ numericstring ] "(" key-string ")"
key-string = *key-char
key-char = <a-z, A-Z, 0-9, and "-">
Kille [page 142]
RFC 1327bis
MIXER DRAFT Version 2.6
object-identifier ::= oid-comp object-identifier
| oid-comp
oid-comp ::= [ key-string ] "(" numericstring ")"
encoded-info = 1#encoded-type
encoded-type = built-in-eit / object-identifier
built-in-eit = "Undefined" ; undefined (0)
/ "Telex" ; tLX (1)
/ "IA5-Text" ; iA5Text (2)
/ "G3-Fax" ; g3Fax (3)
/ "TIF0" ; tIF0 (4)
/ "Teletex" ; tTX (5)
/ "Videotex" ; videotex (6)
/ "Voice" ; voice (7)
/ "SFD" ; sFD (8)
/ "TIF1" ; tIF1 (9)
encoded-pn = [ given "." ] *( initial "." ) surname
given = 2*<ps-char not including ".">
initial = ALPHA
surname = printablestring
std-or-address = 1*( "/" attribute "=" value ) "/"
attribute = standard-type
/ "RFC-822"
/ dd-key "." std-printablestring
Kille [page 143]
RFC 1327bis
MIXER DRAFT Version 2.6
std-or-address-input = [ sep pair ] sep pair *( sep pair )
sep [ pair sep ]
sep = "/" / ";"
pair = input-attribute "=" value
input-attribute = attribute
/ dd-key ":" std-printablestring
standard-type = key-string
dd-key = key-string
value = std-printablestring
std-printablestring
= *( std-char / std-pair )
std-char = <"{", "}", "*", and any ps-char
except "/" and "=" >
std-pair = "$" ps-char
global-id = std-or-address
mta-field = "X400-Received" ":" x400-trace
/ "Deferred-Delivery" ":" date-time
/ "Latest-Delivery-Time" ":" date-time
x400-trace = "by" md-and-mta ";"
[ "deferred until" date-time ";" ]
[ "converted" "(" encoded-info ")" ";" ]
[ "attempted" md-or-mta ";" ]
action-list
";" arrival-time
Kille [page 144]
RFC 1327bis
MIXER DRAFT Version 2.6
md-and-mta = [ "mta" mta "in" ] global-id
mta = word
arrival-time = date-time
md-or-mta = "MD" global-id
/ "MTA" mta
Action-list = 1#action
action = "Redirected"
/ "Expanded"
/ "Relayed"
/ "Rerouted"
Kille [page 145]
RFC 1327bis
MIXER DRAFT Version 2.6
dr-user-info = dr-summary <CRLF>
dr-recipients <CRLF>
dr-content-return
dr-content-return = "The Original Message is not available"
/ "The Original Message follows:"
dr-summary = "This report relates to your message:" <CRLF>
content-correlator <CRLF> <CRLF>
"of" date-time <CRLF> <CRLF>
dr-recipients = *(dr-recipient <CRLF> <CRLF>)
dr-recipient = dr-recip-success / dr-recip-failure
dr-recip-success =
"Your message was successfully delivered to:"
mailbox "at" date-time
dr-recip-failure = "Your message was not delivered to:"
mailbox <CRLF>
"for the following reason:" *word
report-point = [ "mta" mta-name "in" ] global-id
content-correlator = *word
mta-name = word
Kille [page 146]
RFC 1327bis
MIXER DRAFT Version 2.6
dr-per-message-fields =
/ "X400-Conversion-Date" ":" date-time
/ "X400-Subject-Submision-Identifier" ":"
mts-msg-id
/ "X400-Content-Identifier" ":" printablestring
/ "X400-Content-Type" ":" mts-content-type
/ "X400-Original-Encoded-Information-Types" ":"
encoded-info
/ "X400-Originator-and-DL-Expansion-History" ":"
mailbox ";" date-time ";"
/ "X400-Reporting-DL-Name" ":" mailbox
/ "X400-Content-Correlator" ":" content-correlator
/ "X400-Recipient-Info" ":" recipient-info
/ "X400-Subject-Intermediate-Trace-Information" ":"
x400-trace
/ dr-extensions
dr-per-recipient-fields =
/ "X400-Redirect-Recipient" ":" "x400" ";" std-or
/ "X400-Mapped-Redirect-Recipient" ":" "rfc822" ";" mailbox
/ "X400-Converted-EITs" ":" encoded-info ";"
/ "X400-Delivery-Time" ":" date-time
/ "X400-Type-of-MTS-User" ":" labelled-integer
/ "X400-Last-Trace" ":" [ encoded-info ] date-time
/ "X400-Supplementary-Info" ":"
<"> printablestring <"> ";"
/ "X400-Redirection-History" ":" redirect-history-item
/ "X400-Physical-Forwarding-Address" ":" mailbox
/ "X400-Originally-Specified-Recipient-Number" ":"
integer
/ dr-extensions
dr-extensions = "X400-Discarded-DR-Extensions" ":"
1# (object-identifier / labelled-integer)
dr-diagnostic = "Reason" labelled-integer-2
[ ";" "Diagnostic" labelled-integer-2 ]
Kille [page 147]
RFC 1327bis
MIXER DRAFT Version 2.6
mts-field = "X400-MTS-Identifier" ":" mts-msg-id
/ "X400-Originator" ":" mailbox
/ "X400-Recipients" ":" 1#mailbox
/ "Original-Encoded-Information-Types" ":"
encoded-info
/ "X400-Content-Type" ":" mts-content-type
/ "X400-Content-Identifier" ":" printablestring
/ "Priority" ":" priority
/ "Originator-Return-Address" ":" 1#mailbox
/ "DL-Expansion-History" ":" mailbox ";" date-time ";"
/ "Conversion" ":" prohibition
/ "Conversion-With-Loss" ":" prohibition
/ "Delivery-Date" ":" date-time
/ "Discarded-X400-MTS-Extensions" ":"
1#( object-identifier / labelled-integer )
prohibition = "Prohibited" / "Allowed"
mts-msg-id = "[" global-id ";" *text "]"
mts-content-type = "P2" / labelled-integer
/ object-identifier
priority = "normal" / "non-urgent" / "urgent"
Kille [page 148]
RFC 1327bis
MIXER DRAFT Version 2.6
ipn-body-format = ipn-description <CRLF>
[ ipn-extra-information <CRLF> ]
[ ipn-content-return ]
ipn-description = ipn-receipt / ipn-non-receipt
ipn-receipt = "Your message to:" preferred-recipient <CRLF>
"was received at" receipt-time <CRLF> <CRLF>
"This notification was generated"
acknowledgement-mode <CRLF>
"The following extra information was given:" <CRLF>
ipn-suppl <CRLF>
ipn-non-receipt = "Your message to:"
preferred-recipient <CRLF>
ipn-reason
ipn-reason = ipn-discarded / ipn-auto-forwarded
ipn-discarded = "was discarded for the following reason:"
discard-reason <CRLF>
ipn-auto-forwarded = "was automatically forwarded." <CRLF>
[ "The following comment was made:"
auto-comment ]
ipn-extra-information =
"The following information types were converted:"
encoded-info
ipn-content-return = "The Original Message is not available"
/ "The Original Message follows:"
preferred-recipient = mailbox
receipt-time = date-time
auto-comment = printablestring
ipn-suppl = printablestring
Kille [page 149]
RFC 1327bis
MIXER DRAFT Version 2.6
discard-reason = "Expired" / "Obsoleted" /
"User Subscription Terminated" / "IPM Deleted"
acknowledgement-mode = "Manually" / "Automatically"
ipms-field = "Supersedes" ":" 1*msg-id
/ "Expires" ":" date-time
/ "Reply-By" ":" date-time
/ "Importance" ":" importance
/ "Sensitivity" ":" sensitivity
/ "Autoforwarded" ":" boolean
/ "Incomplete-Copy" ":"
/ "Content-Language" ":" 1#language
/ "Message-Type" ":" message-type
/ "Discarded-X400-IPMS-Extensions" ":" 1#object-identifier
/ "Autosubmitted" ":" autosubmitted
importance = "low" / "normal" / "high"
sensitivity = "Personal" / "Private" /
"Company-Confidential"
language = 2*ALPHA [ "(" language-description ")" ]
language-description = printable-string
message-type = "Delivery Report"
/ "InterPersonal Notification"
/ "Multiple Part"
autosubmitted = "not-auto-submitted"
/ "auto-generated"
/ "auto-replied"
/ "auto-forwarded"
Kille [page 150]
RFC 1327bis
MIXER DRAFT Version 2.6
redirect-comment = redirect-first *( redirect-subsequent )
redirect-first = "Originally To:" mailbox "Redirected on"
date-time "To:" redirection-reason
redirect-subsequent = mailbox "Redirected Again on"
date-time "To:" redirection-reason
redirection-history-item = "intended recipient" mailbox
"redirected to" redirection-reason
"on" date-time
redirection-reason =
"Recipient Assigned Alternate Recipient"
/ "Originator Requested Alternate Recipient"
/ "Recipient MD Assigned Alternate Recipient"
/ "Directory Look Up"
/ "Alias"
subject-line = "Delivery-Report" "(" status ")"
[ "for" destination ]
status = "success" / "failure" / "success and failures"
destination = mailbox / "MTA" word
extended-heading =
"Prevent-NonDelivery-Report" ":"
/ "Generate-Delivery-Report" ":"
/ "Alternate-Recipient" ":" prohibition
/ "Disclose-Recipients" ":" prohibition
/ "X400-Content-Return" ":" prohibition
Kille [page 151]
RFC 1327bis
MIXER DRAFT Version 2.6
Appendix F - Text format for MCGAM distribution
1. Text Formats
This appendix defines text formats for exchange of four types of
mapping.
1. Domain Name Space -> OR Address Space MCGAM
2. OR Address Space -> Domain Name Space MCGAM
3. Domain Name Space -> OR Address of preferred gateway
4. OR Address Space -> Domain Name of preferred gateway
2. Mechanisms to register and to distribute MCGAMs
There is a well known set of MCGAM tables.
The global coordination of the mapping rules is a part of the
DANTE MailFLOW Project. New mapping rules may be defined by the
authority responsible for the relevant name space. The rules need
to be registered with a national mapping registration authority,
which in turn passes them on to the central mapping registration
authority. All the collected mapping rules are merged together
into the globally coordinated mapping tables by the MailFLOW
Project Team. The tables are available from the national mapping
registration authorities.
To get a contact address of the mapping registration authority
for the respective country or more information about the MailFLOW
Project contact:
Kille [page 152]
RFC 1327bis
MIXER DRAFT Version 2.6
SWITCH
MailFLOW Project Team
Limmatquai 138
8001 Zuerich
Switzerland
email: mailflow@mailflow.dante.net
S=MailFLOW;O=MailFLOW;P=DANTE;A=mailnet;C=fi;
fax: +41 1 268 15 68
tel: +41 1 268 15 20
3. Syntax Definitions
An address syntax is defined, which is compatible with the syntax
used for 822.domains. By representing the OR addresses as
domains, all lookups can be mechanically implemented as domain ->
domain mappings. This syntax defined is initially for use in
table format, but the syntax is defined in a manner which makes
it suitable to be adapted for use with the Domain Name Service.
This syntax allows for a general representation of OR addresses,
so that it can be used in other applications. Not all attributes
are used in the table formats defined.
To allow the mapping where a level of the hierarchy is
omitted, the pseudo-value "@" (not a printable string character)
is used to indicate omission of a level in the hierarchy. This
is distinct from the form including the element with no value,
although a correct X.400 implementation will interpret both in
the same manner.
This syntax is not intended to be handled by users.
Kille [page 153]
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MIXER DRAFT Version 2.6
dmn-or-address = dmn-part *( "." dmn-part )
mn-part = dmn-attribute "$" value
dmn-attribute = standard-type
/ "~" dmn-printablestring
value = dmn-printablestring
/ "@"
dmn-printablestring =
= *( dmn-char / dmn-pair )
dmn-char = <"{", "}", "*", and any ps-char
except ".">
dmn-pair = "\."
An example usage:
~ROLE$Big\.Chief.ADMD$ATT.C$US
PRMD$DEC.ADMD$@.C$US
The first example illustrates quoting of a "." and a domain
define attribute (ROLE). The second example illustrates
omission of the ADMD level. There shall be a strict ordering of
all components in this table, with the most significant
components on the RHS. This allows the encoding to be treated
as a domain.
Various further restrictions are placed on the usage of
dmn-or-address in the address space mapping tables.
a. Only C, ADMD, PRMD, O, and up to four OUs may be used.
b. No components shall be omitted from this hierarchy, although
the hierarchy may terminate at any level. If the mapping is
to an omitted component, the "@" syntax is used.
4. Table Lookups
When determining a match, there are aspects which apply to all
lookups. Matches are always case independent. The key for all
three tables is a domain. The longest possible match shall be
obtained. Suppose the table has two entries with the following
keys:
K.L
J.K.L
Kille [page 154]
RFC 1327bis
MIXER DRAFT Version 2.6
Domain "A.B.C" will not return any matches. Domain "I.J.K.L"
will match the entry "J.K.L:.
5. Domain -> OR Address MCGAM format
The BNF is:
domain-syntax "#" dmn-or-address "#"
EBNF.domain-syntax is defined in Section 4.2. Note that the
trailing "#" is used for clarity, as the dmn-or-address syntax
might lead to values with trailing blanks. Lines starting with
"#" are comments.
For example:
AC.UK#PRMD$UK\.AC.ADMD$GOLD 400.C$GB#
XEROX.COM#O$Xerox.ADMD$ATT.C$US#
GMD.DE#O$@.PRMD$GMD.ADMD$DBP.C$DE#
A domain is looked up to determine the top levels of an OR
Address. Components of the domain which are not matched are used
to build the remainder of the OR address, as described in Section
4.3.4.
6. OR Address -> Domain MCGAM format
The syntax of this table is:
dmn-or-address "#" domain-syntax "#"
For example:
#
# Mapping table
#
PRMD$UK\.AC.ADMD$GOLD 400.C$GB#AC.UK#
The OR Address is used to generate a domain key. It is important
to order the components correctly, and to fill in missing
components in the hierarchy. Use of this mapping is described in
Section 4.3.2.
Kille [page 155]
RFC 1327bis
MIXER DRAFT Version 2.6
7. Domain -> OR Address of Preferred Gateway table
This uses the same format as the domain -> OR address MCGAM
table. In this case, the restriction to only use
C/ADMD/PRMD/O/OU does not apply. Use of this mapping is
described in Section 4.3.4. A domain cannot appear in this table
and in the domain to OR Address table.
8. OR Addresss -> domain of Preferred Gateway table
This uses the same format as the OR Address -> domain MCGAM
table. Use of this mapping is described in Section 4.3.5. An OR
Address cannot appear in this table and in the OR Address to
domain table.
Kille [page 156]
RFC 1327bis
MIXER DRAFT Version 2.6
Appendix G - Conformance
This appendix defines a number of options, which a conforming
gateway shall specify. Conformance to this specification shall
not be claimed if any of the mandatory features are not
implemented. A specification of conformance may list the service
elements of Chapter 2, in order to be clear that full conformance
is provied. In particular:
- Formats for all fields shall be followed.
- The gateway shall enable MCGAMs to be used.
- Formats for subject lines, delivery reports and IPNs shall
be followed. A system which followed the syntax, but
translated text into a language other than english would be
conformant.
- RFC 1137 shall not be followed when mapping to SMTP.
- All mappings of trace shall be implemented.
- There shall be a mechanism to access all three global
mappings.
- RFC 1494bis shall be followed for mapping body parts.
- When it is specified that a MIME format message is
generated, RFC 1521 shall be followed.
A gateway shall specify:
- Which Interent Message Transport (822-MTS) protocols are
supported. If SMTP is supported, Appendex A of MIXER shall
be used.
- Which X.400 versions are supported (84, 88, 92).
- Which mechanisms (table, X.500, DNS) are supported to access
MCGAMs.
- The mechanism or mechanisms by which the global mapping
information is accessed.
Kille [page 157]
RFC 1327bis
MIXER DRAFT Version 2.6
The following are optional parts of this specification. A
conforming implementation shall specify which of these it
supports.
- Support for the extension mappings of Appendix C.
- Support for returning illegal format content in a delivery
report
- Which address interpretation heuristics are supported
(4.3.4.1)
- If RFC 987 generated message ids are handled in a backwards
compatible manner (4.7.3.6)
Kille [page 158]
RFC 1327bis
MIXER DRAFT Version 2.6
Appendix H - Change History: RFC 987, 1026, 1138, 1148
RFC 987 was the original document, and contained the key elements
of this specification. It was specific to X.400(1984). RFC 1026
specified a small number of necessary changes to RFC 987.
RFC 1138 was based on the RFC 987 work. It contained an
editorial error, and was reissued a few months later as RFC 1148.
RFC 1148 will be referred to here, as it is the document which is
widely referred to elsewhere. The major goal of RFC 1148 was to
upgrade RFC 987 to X.400(1988). It did this, but did not
obsolete RFC 987, which was recommended for use with X.400(1984).
This appendix summarises the changes made in going from RFC 987
to RFC 1148.
RFC 1148 noted the following about its upgrade from RFC 987:
Unnecessary change is usually a bad idea. Changes on the RFC 822
side are avoided as far as possible, so that RFC 822 users do
not see arbitrary differences between systems conforming to this
specification, and those following RFC 987. Changes on the X.400
side are minimised, but are more acceptable, due to the mapping
onto a new set of services and protocols.
1. Introduction
The model has shifted from a protocol based mapping to a service
based mapping. This has increased the generality of the
specification, and improved the model. This change affects the
entire document.
A restriction on scope has been added.
2. Service Elements
- The new service elements of X.400 are dealt with.
- A clear distinction is made between origination and
reception
Kille [page 159]
RFC 1327bis
MIXER DRAFT Version 2.6
3. Basic Mappings
- Add teletex support
- Add object identifier support
- Add labelled integer support
- Make PrintableString <-> ASCII mapping reversible
- The printable string mapping is aligned to the NBS mapping
derived from RFC 987.
4. Addressing
- Support for new addressing attributes
- The message ID mapping is changed to not be table driven
5. Detailed Mappings
- Define extended IPM Header, and use instead of second body
part for RFC 822 extensions
- Realignment of element names
- New syntax for reports, simplifying the header and
introducing a mandatory body format (the RFC 987 header
format was unusable)
- Drop complex autoforwarded mapping
- Add full mapping for IP Notifications, defining a body
format
- Adopt an MTS Identifier syntax in line with the OR Address
syntax
- A new format for X400 Trace representation on the RFC 822
side
Kille [page 160]
RFC 1327bis
MIXER DRAFT Version 2.6
6. Appendices
- Move Appendix on restricted 822 mappings to a separate RFC
- Delete Phonenet and SMTP Appendixes
Kille [page 161]
RFC 1327bis
MIXER DRAFT Version 2.6
Appendix I - Change History: RFC 1148 to RFC 1327
1. General
- The scope of the document was changed to cover X.400(1984),
and so obsolete RFC 987.
- Changes were made to allow usage to connect RFC 822 networks
using X.400
- Text was tightened to be clear about optional and mandatory
aspects
- A good deal of clarification
- A number of minor EBNF errors
- Better examples are given
- Further X.400 upper bounds are handled correctly
2. Basic Mappings
- The encoding of object identifier is changed slightly
3. Addressing
- A global mapping of domain to preferred gateway is
introduced.
- An overflow mechanism is defined for RFC 822 addresses of
greater than 128 bytes
- Changes were made to improve compatibility with the PDAM on
writing OR Addresses.
+ The PD and Terminal Type keywords were aligned to the
PDAM. It is believed that minimal use has been made of
the RFC 1148 keywords.
Kille [page 162]
RFC 1327bis
MIXER DRAFT Version 2.6
+ P and A are allowed as alternate keys for PRMD and ADMD
+ Where keywords are different, the PDAM keywords are
alternatives on input. This is mandatory.
4. Detailed Mappings
- The format of the Subject: lines is defined.
- Illegal use (repetition) of the heading EXTENSION is
corrected, and a new object identifier assigned.
- The Delivery Report format is extensively revised in light
of operational experience.
- The handling of redirects is significantly changed, as the
previous mechanism did not work.
5. Appendices
- An SMTP appendix is added, allowing optional use of the VRFY
command to improve probe information.
- Handling of JNT Mail Acknowledge-To is changed slightly.
- A DDA JNT-MAIL is allowed on input.
- The format definitions of Appendix F are explained further,
and a third table definition added.
- An appendix on use with X.400(1984) is added.
- Optional extensions are defined to give RFC 822 access to
further X.400 facilities.
- An appendix on conformance is added.
Kille [page 163]
RFC 1327bis
MIXER DRAFT Version 2.6
Appendix J - Change History: RFC 1327 to this Document
1. General
This update is primarily for stability, and to fold in
compatibility for MIME and to add support for the new NOTARY
delivery status notifications. Other general changes:
- Various editorial updates
- Minor EBNF errors
- Reference to mapping table support by DNS and X.500.
- Alignment to X.400(92)
- Assignment of a new object identifier
- Removal of specification relating to body mapping, which is
now defined in RFC 1494bis.
2. Service Elements
- Support of Auto-Submitted service
3. Basic Mappings
- Comments shall not be used in new headers, to remove parsing
ambiguity
- RFC 1522 encoding may be used as an alternative to X.408
downgrade, where appropriate.
- Correct handling of RFC 822 four year dates.
4. Addressing
- Replaced the mandatory global address mapping with MCGAMs.
Kille [page 164]
RFC 1327bis
MIXER DRAFT Version 2.6
- Add codes and add a heuristic to align to the standard X.400
form of writing OR Addresses.
- Improved text on ordering heuristic
- Leading "/" interpretation added
- All bar one of the address mapping heuristics made
mandatory.
- Interpretation of domain defined attribute "RFC-822" made
mandatory in all cases
- Make report request comments optional
5. Detailed Mappings
- Comments no longer maps to separate body part
- Allow Languages to be multi-valued
- Change Content-Identifier to X400-Content-Identifier, in
order to avoid confusion with MIME.
- Reverse mapping of MIXER defined fields made mandatory
- "Expiry-Date:" changed to "Expires:".
- "Obsoletes:" changed to "Supersedes:".
- Define correct handling when "Resent-Date:" is present.
6. Appendices
- Change "Content-Return" to "X400-Content-Return" in Appendix
C.
- Relaxation of restrictions on mapping 3 in Appendix F.
- Add linkage to HARPOON in Appendix B.
- RFC 1494bis added to the conformance statement of Appendix
Kille [page 165]
RFC 1327bis
MIXER DRAFT Version 2.6
G.
- Added Appendix L, with ASN. Summary.
Kille [page 166]
RFC 1327bis
MIXER DRAFT Version 2.6
Appendix L - ASN.1 Summary
MIXER Definitions { iso org(3) dod(6) internet(1) mail(7)
mixer(1) mixer-core(3) definitions(1) }
DEFINITIONS IMPLICIT TAGS ::=
BEGIN
-- exports everything
IMPORTS
EXTENSION FROM
MTSAbstractService {join-iso-ccit mhs-motis(6) mts(3)
modules(0) mts-abstract-service(1) }
HEADING-EXTENSION FROM
IPMSAbstractService {join-iso-ccit mhs-motis(6) ipms(1)
modules(0) abstract-service(3) }
rfc-822-field HEADING-EXTENSION
VALUE RFC822FieldList
::= id-rfc-822-field-list
RFC822FieldList ::= SEQUENCE OF RFC822Field
RFC822Field ::= IA5String
dsn-header-list EXTENSION
RFC822FieldList
::= id-dsn-header-list
dsn-field-list EXTENSION
RFC822FieldList
::= id-dsn-field-list
Kille [page 167]
RFC 1327bis
MIXER DRAFT Version 2.6
internet ::= OBJECT IDENTIFIER { iso org(3) dod(6) 1 } -- from RFC 1155
mail OBJECT IDENTIFIER ::= { internet 7 } -- IANA assigned
mixer OBJECT IDENTIFIER ::= { mail mixer(1) } -- inherited from RFC 1495
mixer-core OBJECT IDENTIFIER ::= { mixer core(3) }
id-rfc-822-field-list OBJECT IDENTIFIER ::= {mixer-core 2}
id-dsn-header-list OBJECT IDENTIFIER ::= {mixer-core 3}
id-dsn-field-list OBJECT IDENTIFIER ::= {mixer-core 4}
eit-mixer OBJECT IDENTIFIER ::= {mixer-core 5}
-- the MIXER pseudo-EIT
END -- MIXER ASN.1
Kille [page 168]
RFC 1327bis
MIXER DRAFT Version 2.6
SECURITY CONSIDERATIONS
Security considerations are not discussed in this RFC.
AUTHOR'S ADDRESS
Steve Kille
Isode Ltd
The Dome
The Square
Richmond
TW9 1DT
England
Phone: +44-181-332-9091
Internet EMail: S.Kille@ISODE.COM
X.400 Email: I=S; S=Kille; P=Isode; A=Mailnet; C=FI;
UFN: S.Kille, Isode, GB
Kille [page 169]
RFC 1327bis
MIXER DRAFT Version 2.6
References
1. CCITT , "Recommendations X.400," Message Handling Systems:
System Model - Service Elements, Oct 1984.
2. C. Allocchio, "MaXIM11 - Mapping between X.400 / Internet
Mail and Mail-11 mail," RFC 1405bis, Jan 1997.
3. C. Allocchio, "Using the Internet DNS to Distribute MIXER
Conformant Global Address Mapping (MCGAM)," RFC 1664bis, Jan
1997.
4. H.T. Alvestrand, S.E. Kille, R. Miles, M. Rose, and S.
Thompson, "Mapping between X.400 and RFC-822 Message
Bodies," RFC 1495, Aug 1993.
5. H.T. Alvestrand, J. Romaguera, and K. Jordan, "Rules for
Downgrading Messages for X.400(88) to X.400(84) When MIME
Content-Types are Present in the Messages (Harpoon)," RFC
1496, Aug 1993.
6. H.T. Alvestrand and S. Thompson, "Equivalences between X.400
and RFC-822 Message Bodies," RFC 1494, Aug 1993.
7. H.T. Alvestrand, "Tags for the Identification of Languages,"
RFC 1756, Mar 1995.
8. H.T. Alvestrand, "Mapping between X.400 and RFC-822/MIME
Message Bodies," RFC Draft, Aug 1996.
9. N. Borenstein and N. Freed, "MIME (Multipurpose Internet
Mail Extensions)," RFC 1521, Sep 1993.
10. R.T. Braden, "Requirements for Internet Hosts -- Application
and Support," RFC 1123, Oct 1989.
11. CCITT/ISO, "CCITT Recommendations X.420/ ISO/IEC 10021-7,"
Message Handling Systems: Interpersonal Messaging System,
Dec 1988.
12. CCITT/ISO, "CCITT Recommendations X.411/ ISO/IEC 10021-4,"
Message Handling Systems: Message Transfer System: Abstract
Service Definition and Procedures, Dec 1988.
Kille [page 170]
RFC 1327bis
MIXER DRAFT Version 2.6
13. CCITT/ISO, "CCITT Recommendations X.400/ ISO/IEC 10021-1,"
Message Handling: System and Service Overview , Dec 1988.
14. CCITT/ISO, "Specification of Abstract Syntax Notation One
(ASN.1)," CCITT Recommendation X.208 / ISO/IEC 8824, Dec
1988.
15. CCITT/ISO, "CCITT Recommendations X.400/ ISO/IEC 10021-1,"
Message Handling: System and Service Overview , Dec 1992.
16. D.H. Crocker, "Standard of the Format of ARPA Internet Text
Messages," RFC 822, Aug 1982.
17. S.E. Kille, "Mapping Between X.400 and RFC 822," UK Academic
Community Report (MG.19) / RFC 987, Jun 1986.
18. S.E. Kille, "Addendum to RFC 987," UK Academic Community
Report (MG.23) / RFC 1026, Aug 1987.
19. S.E. Kille, "Mapping Between X.400(1988) / ISO 10021 and RFC
822," RFC 1138, Oct 1989.
20. S.E. Kille, "Mapping Between X.400(1988) / ISO 10021 and RFC
822," RFC 1148, Mar 1990.
21. S.E. Kille, "Mapping Between X.400(1988) / ISO 10021 and RFC
822," RFC 1327, May 1992.
22. S.E. Kille, "X.400 1988 to 1984 downgrading," RFC 1328, May
1992.
23. S.E. Kille, "A String Encoding of Presentation Address," RFC
1278, Nov 1992.
24. S.E. Kille, "A String Representation of Distinguished Name,"
RFC 1485, Jan 1992.
25. S.E. Kille, "Using the OSI Directory to achieve User
Friendly Naming," RFC 1484, Jan 1992.
26. S.E. Kille, "Use of an X.500/LDAP directory to support MIXER
address mapping," RFC 1838bis, Feb 1997.
27. N. Koorland, "Message Attachmment Work Group (MAWG): MAWG
Kille [page 171]
RFC 1327bis
MIXER DRAFT Version 2.6
Feasibility Project Guide," EMA Report, Version 1.5, Nov
1995.
28. K. Moore and G. Vaudreuil, "An Extensible Message Format for
Delivery Status Notifications," RFC 1894, Jan 1996.
29. K. Moore, "SMTP Service Extensions for Delivery Status
Notifications," RFC 1891, Jan 1996.
30. J.B. Postel, "SIMPLE MAIL TRANSFER PROTOCOL," RFC 821, Aug
1982.
Kille [page 172]