Internationalized Email Headers
draft-ietf-eai-utf8headers-12
The information below is for an old version of the document that is already published as an RFC.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 5335.
|
|
|---|---|---|---|
| Author | Abel Yang | ||
| Last updated | 2020-01-21 (Latest revision 2008-07-10) | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | Experimental | ||
| Formats | |||
| Reviews | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | WG Document | |
| Document shepherd | (None) | ||
| IESG | IESG state | Became RFC 5335 (Experimental) | |
| Action Holders |
(None)
|
||
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | Chris Newman | ||
| Send notices to | draft-ietf-eai-smtpext@ietf.org |
draft-ietf-eai-utf8headers-12
Network Working Group Y. Abel, Ed.
Internet-Draft TWNIC
Intended status: Experimental July 09, 2008
Expires: January 10, 2009
Internationalized Email Headers
draft-ietf-eai-utf8headers-12.txt
Status of this Memo
By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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other groups may also distribute working documents as Internet-
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and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
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This Internet-Draft will expire on January 10, 2009.
Abstract
Full internationalization of electronic mail requires not only the
capability to transmit non-ASCII content, to encode selected
information in specific header fields, and to use non-ASCII
characters in envelope addresses. It also requires being able to
express those addresses and information based on them in mail header
fields. This document specifies an experimental variant of Internet
mail that permits the use of Unicode encoded in UTF-8, rather than
ASCII, as the base form for Internet email header field bodies. This
form is permitted in transmission only if authorized by an SMTP
extension, as specified in an associated specification. And this
specification updates section 6.4 of [RFC2045] to conform with the
requirements.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Role of this specification . . . . . . . . . . . . . . . . 3
1.2. Relation to other standards . . . . . . . . . . . . . . . 3
2. Background and History . . . . . . . . . . . . . . . . . . . . 3
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Changes on Message Header Fields . . . . . . . . . . . . . . . 5
4.1. UTF8 Syntax and Normalization . . . . . . . . . . . . . . 5
4.2. Changes on MIME headers . . . . . . . . . . . . . . . . . 6
4.3. Syntax extensions to RFC 2822 . . . . . . . . . . . . . . 6
4.4. Change on addr-spec syntax . . . . . . . . . . . . . . . . 8
4.5. Trace field syntax . . . . . . . . . . . . . . . . . . . . 9
4.6. message/global . . . . . . . . . . . . . . . . . . . . . . 9
5. Security Considerations . . . . . . . . . . . . . . . . . . . 11
6. IANA considerations . . . . . . . . . . . . . . . . . . . . . 12
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12
8. Edit history . . . . . . . . . . . . . . . . . . . . . . . . . 12
8.1. draft-ietf-eai-utf8header-12 . . . . . . . . . . . . . . . 12
8.2. draft-ietf-eai-utf8header-11 . . . . . . . . . . . . . . . 12
8.3. draft-ietf-eai-utf8header-10 . . . . . . . . . . . . . . . 12
8.4. draft-ietf-eai-utf8header-09 . . . . . . . . . . . . . . . 13
8.5. draft-ietf-eai-utf8header-08 . . . . . . . . . . . . . . . 13
8.6. draft-ietf-eai-utf8header-07 . . . . . . . . . . . . . . . 13
8.7. draft-ietf-eai-utf8header-06 . . . . . . . . . . . . . . . 13
8.8. draft-ietf-eai-utf8header-05 . . . . . . . . . . . . . . . 13
8.9. draft-ietf-eai-utf8header-04 . . . . . . . . . . . . . . . 13
8.10. draft-ietf-eai-utf8header-03 . . . . . . . . . . . . . . . 13
8.11. draft-ietf-eai-utf8header-02 . . . . . . . . . . . . . . . 14
8.12. draft-ietf-eai-utf8header-01 . . . . . . . . . . . . . . . 14
8.13. draft-ietf-eai-utf8header-00 . . . . . . . . . . . . . . . 14
8.14. draft-yeh-ima-utf8header-01 . . . . . . . . . . . . . . . 14
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
9.1. Normative References . . . . . . . . . . . . . . . . . . . 14
9.2. Informative References . . . . . . . . . . . . . . . . . . 15
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 15
Intellectual Property and Copyright Statements . . . . . . . . . . 17
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1. Introduction
1.1. Role of this specification
Full internationalization of electronic mail requires several
capabilities:
o The capability to transmit non-ASCII content, provided for as part
of the basic MIME specification [RFC2045], [RFC2046].
o The capability to use international characters in envelope
addresses, discussed in [RFC4952] and specified in
[I-D.ietf-eai-smtpext].
o The capability to express those addresses, and information related
to them and based on them, in mail header fields, defined in this
document.
This document specifies an experimental variant of Internet mail that
permits the use of Unicode encoded in UTF-8 [RFC3629], rather than
ASCII, as the base form for Internet email header fields. This form
is permitted in transmission, if authorized by the SMTP extension
specified in [I-D.ietf-eai-smtpext] or by other transport mechanisms
capable of processing it.
1.2. Relation to other standards
This document updates section 6.4 of RFC 2045. It removes the
blanket ban on applying a content-transfer-encoding to all subtypes
of message/, and instead specifies that a composite subtype MAY
specify whether or not a content-transfer-encoding can be used for
that subtype, with "cannot be used" as the default.
This document also updates [RFC2822] and MIME ([RFC2045]), and the
fact that an experimental specification updates a standards-track
spec means that people who participate in the experiment have to
consider those standards updated.
Allowing of use a content-transfer-encoding on subtypes of messages
is not limited to transmissions, which are authorized by the SMTP
extension specified in [I-D.ietf-eai-smtpext]. Message/global
permits use of a content-transfer-encoding.
2. Background and History
Mailbox names often represent the names of human users. Many of
these users throughout the world have names that are not normally
expressed with just the ASCII repertoire of characters, and would
like to use more or less their real names in their mailbox names.
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These users are also likely to use non-ASCII text in their common
names and subjects of email messages, both in what they send and what
they receive. This protocol specifies UTF-8 as the encoding to
represent email header field bodies.
The traditional format of email messages [RFC2822] allows only ASCII
characters in the header fields of messages. This prevents users
from having email addresses that contain non-ASCII characters. It
further forces non-ASCII text in common names, comments, and in free
text (such as in the Subject: field) to be encoded (as required by
MIME format [RFC2047]). This specification describes a change to the
email message format that is related to the SMTP message transport
change described in the associated document [RFC4952] and
[I-D.ietf-eai-smtpext], and that allows non-ASCII characters in most
email header fields. These changes affect SMTP clients, SMTP
servers, mail user agents (MUAs), list expanders, gateways to other
media, and all other processes that parse or handle email messages.
As specified in [I-D.ietf-eai-smtpext], an SMTP protocol extension
"UTF8SMTP" is used to prevent the transmission of messages with UTF-8
header fields to systems that cannot handle such messages.
Use of this SMTP extension helps prevents the introduction of such
messages into message stores that might misinterpret, improperly
display, or mangle such messages. It should be noted that using an
ESMTP extension does not prevent transfering email messages with
UTF-8 header fields to other systems that use the email format for
messages and that may not be upgraded, such as unextended POP and
IMAP servers. Changes to these protocols to handle UTF-8 header
fields are addressed in [I-D.ietf-eai-pop] and
[I-D.ietf-eai-imap-utf8] .
The objective for this protocol is to allow UTF-8 in email header
fields. Issues such as how to handle messages containing UTF-8
header fields that have to be delivered to systems that have not been
upgraded to support this capability are discussed in
[I-D.ietf-eai-downgrade].
3. Terminology
A plain ASCII string is also a valid UTF-8 string, see [RFC3629]. In
this document, ordinary ASCII characters are UTF-8 characters if they
are in headers which contain <utf8-xtra-char>s.
Unless otherwise noted, all terms used here are defined in [RFC2821],
[RFC2822], [RFC4952], or [I-D.ietf-eai-smtpext].
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The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
This document is discussed on the ima mailing list. See
https://www1.ietf.org/mailman/listinfo/ima for information about
subscribing. The list's archive is at
http://www1.ietf.org/mail-archive/web/ima/index.html.
4. Changes on Message Header Fields
SMTP clients can send header fields in UTF-8 format, if the UTF8SMTP
extension is advertised by the SMTP server or as permitted by other
transport mechanisms.
This protocol does NOT change the [RFC2822] rules for defining header
field names. The bodies of header fields are allowed to contain
UTF-8 characters, but the header field names themselves must contain
only ASCII characters.
To permit UTF-8 characters in field values, the header definition in
[RFC2822] must be extended to support new format. The following ABNF
is defined to substitute those definition in [RFC2822].
The syntax rules not covered in this section remain as defined in
[RFC2822].
4.1. UTF8 Syntax and Normalization
UTF-8 characters can be defined in terms of octets using the
following ABNF, taken from [RFC3629]:
UTF8-xtra-char = UTF8-2 / UTF8-3 / UTF8-4
UTF8-2 = %xC2-DF UTF8-tail
UTF8-3 = %xE0 %xA0-BF UTF8-tail /
%xE1-EC 2(UTF8-tail) /
%xED %x80-9F UTF8-tail /
%xEE-EF 2(UTF8-tail)
UTF8-4 = %xF0 %x90-BF 2( UTF8-tail ) /
%xF1-F3 3( UTF8-tail ) /
%xF4 %x80-8F 2( UTF8-tail )
UTF8-tail = %x80-BF
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These are normatively defined in [RFC3629], but kept in this document
for reasons of convenience.
See [RFC5198] for a discussion of normalization, the use of
normalization form NFC is RECOMMENDED.
4.2. Changes on MIME headers
This specification updates section 6.4 of [RFC2045]. [RFC2045]
prohibits applying a content-transfer-encoding to all subtypes of
message/. This specification relaxes the rule, allowing newly
defined MIME types to permit content-transfer-encoding, and permits
content-transfer-encoding for message/global (see Section 4.6).
Background: Normally, transfer of message/global will be done in
8-bit-clean channels, and body parts will have "identity" encodings,
that is, no decoding is necessary. In the case where a message
containing a message/global is downgraded from 8-bit to 7-bit as
described in [RFC1652]., an encoding may be applied to the message;
if the message travels multiple times between a 7-bit environment and
an environment implementing UTF8SMTP, multiple levels of encoding may
occur. This is expected to be rarely seen in practice, and the
potential complexity of other ways of dealing with the issue are
thought to be larger than the complexity of allowing nested encodings
where necessary.
4.3. Syntax extensions to RFC 2822
The following rules intended to extend the corresponding rules in
[RFC2822] to allow UTF8 characters.
FWS = <see [RFC 2822], folding white space>
CFWS = <see [RFC 2822], folding white space>
ctext =/ UTF8-xtra-char
utext =/ UTF8-xtra-char
comment = "(" *([FWS] utf8-ccontent) [FWS] ")"
word = utf8-atom / utf8-quoted-string
This means that all the [RFC2822] constructs that build upon these
will permit UTF-8 characters, including comments and quoted strings.
We do not change the syntax of <atext> in order to allow UTF8
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characters in <addr-spec>, because this would also allow UTF8
characters in <message-id>, it is not allowed due to the limitation
described in Section 4.5. Instead, <utf8-atext> is added to meet
this requirement.
utf8-text = %d1-9 / ; all UTF-8 characters except
%d11-12 / ; US-ASCII NUL, CR and LF
%d14-127 /
UTF8-xtra-char
utf8-quoted-pair = ("\" utf8-text) / obs-qp
utf8-qcontent = utf8-qtext / utf8-quoted-pair
utf8-quoted-string = [CFWS]
DQUOTE *([FWS] utf8-qcontent) [FWS] DQUOTE
[CFWS]
utf8-ccontent = ctext / utf8-quoted-pair / comment
utf8-qtext= qtext / UTF8-xtra-char
utf8-atext = ALPHA / DIGIT /
"!" / "#" / ; Any character except
"$" / "%" / ; controls, SP, and specials.
"&" / "'" / ; Used for atoms
"*" / "+" /
"-" / "/" /
"=" / "?" /
"^" / "_" /
"`" / "{" /
"|" / "}" /
"~" /
UTF8-xtra-char
utf8-atom = [CFWS] 1*utf8-atext [CFWS]
utf8-dot-atom = [CFWS] utf8-dot-atom-text [CFWS]
utf8-dot-atom-text = 1*utf8-atext *("." 1*utf8-atext)
qcontent = utf8-qcontent
To allow the use of UTF-8 in a Content-Description header field
[RFC2045], the following syntax is used:
description = "Content-Description:" unstructured CRLF
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The <utext> syntax is extended above to allow UTF-8 in all
<unstructured> header fields.
Note, however, this does not remove any constraint on the character
set of protocol elements; for instance, all the allowed values for
timezone in the Date: headers are still expressed in ASCII. And
also, none of this revised syntax changes what is allowed in a
<msg-id>, which will still remain in pure ASCII.
4.4. Change on addr-spec syntax
Internationalized email addresses are represented in UTF-8. Thus,
all header fields containing <mailbox>es are updated to permit UTF-8
as well as an additional, optional all-ascii alternate address. Note
that MSAs and MTAs may downgrade internationalized messages as
needed. The procedure for doing so is described in
[I-D.ietf-eai-downgrade].
mailbox = name-addr / addr-spec / utf8-addr-spec
angle-addr =/ [CFWS] "<" utf8-addr-spec [ alt-address ] ">" [CFWS] /
obs-angle-addr
utf8-addr-spec = utf8-local-part "@" utf8-domain
utf8-local-part= utf8-dot-atom / utf8-quoted-string / obs-local-part
utf8-domain = utf8-dot-atom / domain-literal / obs-domain
alt-address = FWS "<" addr-spec ">"
Below list a few possible <mailbox> representation as example.
"DISPLAY_NAME" <ASCII@ASCII>
; traditional mailbox format
"DISPLAY_NAME" <non-ASCII@non-ASCII>
; UTF8SMTP but no ALT-ADDRESS parameter provided,
; message will bounce if UTF8SMTP extension is not supported
<non-ASCII@non-ASCII>
; without DISPLAY_NAME and quoted string
; UTF8SMTP but no ALT-ADDRESS parameter provided,
; message will bounce if UTF8SMTP extension is not supported
"DISPLAY_NAME" <non-ASCII@non-ASCII <ASCII@ASCII>>
; UTF8SMTP with ALT-ADDRESS parameter provided,
; ALT-ADDRESS can be used if downgrade is necessary
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4.5. Trace field syntax
"For" fields containing internationalized addresses are allowed, by
use of the new uFor syntax. UTF-8 information may be needed in
Received fields. Such information is therefore allowed to preserve
the integrity of those fields. The uFor syntax retains the original
UTF-8 email address between EAI-aware MTAs. Note that, should
downgrading be required, the uFor parameter is dropped per the
procedure specified in [I-D.ietf-eai-downgrade].
The "Return-Path" header provides the email return address in the
mail delivery. Thus, it is augmented to carry UTF8 addresses (see
the revised syntax of <angle-addr> in Section 4.4 of this document).
This will not break the rule of trace field integrity, because it is
added at the last MTA.
The <item-value> on "Received:" syntax is augmented to allow UTF-8
email address on "For" clause. <angle-addr> is augmented to include
UTF-8 email address. To allow UTF-8 email address also on syntax
corresponding of <addr-spec> on original syntax, <utf8-addr-spec> is
added to <item-value>.
item-value =/ utf8-addr-spec
4.6. message/global
Internationalized messages must only be transmitted as authorized by
[I-D.ietf-eai-smtpext] or within a non-SMTP environment which
supports these messages. A message is a "message/global message", if
o it contains UTF-8 header values as specified in this document, or
o it contains UTF-8 values in the headers fields of body parts.
The type message/global is similar to message/rfc822, except that it
contains a message that can contain UTF-8 characters in the headers
of the message or body parts. If this type is sent to a 7-bit-only
system, it has to be encoded in [RFC2045]. (Note that a system
compliant with MIME that doesn't recognize message/global would treat
it as "application/octet-stream" as described in Section 5.2.4 of
[RFC2046].)
Alternatively, SMTP servers and other systems which transfer a
message/global body part MAY choose to down-convert it to a message/
rfc822 body part using the rules described in
[I-D.ietf-eai-downgrade].
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Type name: message
Subtype name: global
Required parameters: none
Optional parameters: none
Encoding considerations: Any content-transfer-encoding is permitted.
The 8-bit or binary content-transfer-encodings are recommended
where permitted.
Security considerations: See Section 5
Interoperability considerations: The media type provides
functionality similar to the message/rfc822 content type for email
messages with international email headers. When there is a need
to embed or return such content in another message, there is
generally an option to use this media type and leave the content
unchanged or downconvert the content to message/rfc822. Both of
these choices will interoperate with the installed base, but with
different properties. Systems unaware of international headers
will typically treat a message/global body part as an unknown
attachment, while they will understand the structure of a message/
rfc822. However, systems which understand message/global will
provide functionality superior to the result of a down-conversion
to message/rfc822. The most interoperable choice depends on the
deployed software.
Published specification: RFC XXXX
Applications that use this media type: SMTP servers and email
clients that support multipart/report generation or parsing.
Email clients which forward messages with international headers as
attachments.
Additional information:
Magic number(s): none
File extension(s): The extension ".u8msg" is suggested.
Macintosh file type code(s): A uniform type identifier (UTI) of
"public.utf8-email-message" is suggested. This conforms to
"public.message" and "public.composite-content" but does not
necessarily conform to "public.utf8-plain-text".
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Person & email address to contact for further information: See the
Author's address section of this document.
Intended usage: COMMON
Restrictions on usage: This is a structured media type which embeds
other MIME media types. The 8-bit or binary content-transfer-
encoding MUST be used unless this media type is sent over a 7-bit
only transport.
Author: See Author's Address section of this document.
Change controller: IETF Standards Process
5. Security Considerations
If a user has a non-ASCII mailbox address and an ASCII mailbox
address, a digital certificate that identifies that user may have
both addresses in the identity. Having multiple email addresses as
identities in a single certificate is already supported in PKIX and
OpenPGP.
Because UTF-8 often requires several octets to encode a single
character, internationalized local parts may cause mail addresses to
become longer. As specified in [RFC2822], each line of characters
MUST be no more 998 octets, excluding the CRLF.
Because internationalized local parts may cause email addresses to be
longer, processes which parse, store, or handle email addresses or
local parts must take extra care not to overflow buffers, truncate
addresses, exceed storage allotments, or, when comparing, fail to use
the entire length.
In this specification, a user could provide an ASCII alternative
address for a non-ASCII address. However, it is possible these two
address go to different mailboxes, or even different persons. This
configuration may be based on a user's personal choice, or based on
administration policy. We recognize that if ASCII and non-ASCII
email is delivered to two different destinations, based on MTA
capability, this may violate the principle of least astonishment, but
this is not a "protocol problem".
The security impact of UTF-8 headers on email signature systems such
as DKIM, S/MIME and OpenPGP is discussed in RFC 4952 section 9. A
subsequent document [I-D.ietf-eai-downgrade] will cover the impact of
downgrading on these systems.
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6. IANA considerations
IANA is asked to register the message/global MIME type using the
registration form contained in Section 4.4.
7. Acknowledgements
This document incorporates many ideas first described in Internet
Draft form by Paul Hoffman, although many details have changed from
that earlier work.
The author especially thank Jeff Yeh for their efforts and
contributions on editing previous versions.
Most of the content of this document is provided by John C Klensin.
Also some significant comments and suggestions were received from
Charles H. Lindsey, Kari Hurtta, Pete Resnick, Alexey Melnikov, Chris
Newman, Yangwoo KO, Yoshiro YONEYA, and other members of the JET team
and were incorporated into the document. The editor is much great
thanks to their contribution sincerely.
8. Edit history
This section is used for tracking the update of this document. Will
be removed after finalize.
8.1. draft-ietf-eai-utf8header-12
1. Sentences modified
2. Update [RFC2045] into the Abstract
3. Update security mechanisms descriptions in Section 5
8.2. draft-ietf-eai-utf8header-11
1. Sentences modified
8.3. draft-ietf-eai-utf8header-10
1. Revise some paragraphs
2. Correct typos of ABNF
3. Note <qtext> and <text> of 2822bis
4. Fixed some idnits warnning
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8.4. draft-ietf-eai-utf8header-09
1. Delete Section 5 (Addtional Issues)
2. Correct two typos of ABNF
3. Refine normalization issue to refer to [RFC5198]
4. Note <qtext> and <text> of 2822bis
5. Revise Section 6
8.5. draft-ietf-eai-utf8header-08
1. Sentences modified
8.6. draft-ietf-eai-utf8header-07
1. Modify subtype message/utf8smtp to message/global
2. Acknowledgements revise
8.7. draft-ietf-eai-utf8header-06
1. ABNF revise.
2. Sentences modified
3. Add paragraph in Section 5
4. Add paragraph in Section 1.2
5. Modify Section 4.6
8.8. draft-ietf-eai-utf8header-05
1. ABNF revise.
2. Remove original the section 4 (Pre-requirement)
3. Add UTF8SMTP message (Section 4.6)
8.9. draft-ietf-eai-utf8header-04
1. ABNF revise.
2. Modify uFor description in Section 4.5
8.10. draft-ietf-eai-utf8header-03
1. Editrial changes on terms and english.
2. ABNF revise.
3. addr-spec change, put ALT-ADDRESS inside "<" and ">" quote with
"<" and ">".
4. Remove the "Header-Type" header.
5. Add uFor description in Section 4.5
6. Remove the content in IANA considerations since "Header-Type" is
removed.
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8.11. draft-ietf-eai-utf8header-02
1. Editrial changes on terms and english.
2. Change the header name "UTF8SMTP" to "Header-Type", and ABNF
revise.
3. addr-spec change, put ALT-ADDRESS inside "<" and ">" quote with
"[" and "]".
4. IANA considerations section rewrite.
8.12. draft-ietf-eai-utf8header-01
1. ABNF revise.
2. Terminology sync with overview document.
3. addr-spec change, put ALT-ADDRESS inside "<" and ">" quote with
"{" and "}".
4. add IANA considerations to register the new 2822 header
"UTF8SMTP".
5. add Security considerations about relation of UTF8SMTP address to
ALT-ADDRESS.
8.13. draft-ietf-eai-utf8header-00
1. ABNF added.
2. Editrial changes.
3. Sent it as WG document.
8.14. draft-yeh-ima-utf8header-01
1. Section re-arranged.
2. Remove content are not below to this document.
9. References
9.1. Normative References
[I-D.ietf-eai-smtpext]
Yao, J. and W. MAO, "SMTP extension for internationalized
email address", draft-ietf-eai-smtpext-12 (work in
progress), April 2008.
[RFC1652] Klensin, J., Freed, N., Rose, M., Stefferud, E., and D.
Crocker, "SMTP Service Extension for 8bit-MIMEtransport",
RFC 1652, July 1994.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
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[RFC2821] Klensin, J., "Simple Mail Transfer Protocol", RFC 2821,
April 2001.
[RFC2822] Resnick, P., "Internet Message Format", RFC 2822,
April 2001.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003.
[RFC4952] Klensin, J. and Y. Ko, "Overview and Framework for
Internationalized Email", RFC 4952, July 2007.
[RFC5198] Klensin, J. and M. Padlipsky, "Unicode Format for Network
Interchange", RFC 5198, March 2008.
9.2. Informative References
[I-D.ietf-eai-downgrade]
Fujiwara, K. and Y. Yoneya, "Downgrading mechanism for
Email Address Internationalization",
draft-ietf-eai-downgrade-07 (work in progress),
March 2008.
[I-D.ietf-eai-imap-utf8]
Resnick, P. and C. Newman, "IMAP Support for UTF-8",
draft-ietf-eai-imap-utf8-03 (work in progress),
April 2008.
[I-D.ietf-eai-pop]
Newman, C. and R. Gellens, "POP3 Support for UTF-8",
draft-ietf-eai-pop-03 (work in progress), February 2008.
[RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message
Bodies", RFC 2045, November 1996.
[RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types", RFC 2046,
November 1996.
[RFC2047] Moore, K., "MIME (Multipurpose Internet Mail Extensions)
Part Three: Message Header Extensions for Non-ASCII Text",
RFC 2047, November 1996.
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Author's Address
Abel Yang (editor)
TWNIC
4F-2, No. 9, Sec 2, Roosvelt Rd.
Taipei, 100
Taiwan
Phone: +886 2 23411313 ext 505
Email: abelyang@twnic.net.tw
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