Postmaster Convention for X.400 Operations
RFC 1648

Document Type RFC - Historic (July 1994; No errata)
Author Allan Cargille 
Last updated 2013-03-02
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Network Working Group                                        A. Cargille
Request for Comments: 1648                       University of Wisconsin
Category: Standards Track                                      July 1994

               Postmaster Convention for X.400 Operations

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.


   Both STD 11, RFC 822 [1] and STD 3, RFC 1123 [2] (Host Requirements)
   require that the email address "postmaster" be supported at all
   hosts.  This paper extends this concept to X.400 mail domains which
   have registered RFC 1327 mapping rules, and which therefore appear to
   have normal RFC822-style addresses.

1.  Postmaster Convention in RFC822

   Operating a reliable, large-scale electronic mail (email) network
   requires cooperation between many mail managers and system
   administrators.  As noted in RFC 822 [1], often mail or system
   managers need to be able to contact a responsible person at a remote
   host without knowing any specific user name or address at that host.
   For that reason, both RFC 822 and the Internet Host Requirements [2]
   require that the address "postmaster" be supported at every Internet

2.  Postmaster Convention and X.400

   However, RFC 822 is not the only email protocol being used in the
   Internet.  Some Internet sites are also running the X.400 (1984) [3]
   and X.400 (1988) [4] email protocols.  RFC 1327 specifies how to map
   between X.400 and RFC 822 addresses [5].  When mapping rules are
   used, addresses map cleanly between X.400 and RFC 822.  In fact, it
   is impossible to determine by inspecting the address whether the
   recipient is an RFC 822 mail user or an X.400 mail user.

   A paper by Rob Hagens and Alf Hansen describes an X.400 community
   known as the "Global Open MHS Community" (GO-MHS) [6].  Many mail
   domains in the GO-MHS Community have registered RFC 1327 mapping
   rules.  Therefore, users in those domains have RFC 822-style email

Cargille                                                        [Page 1]
RFC 1648              X.400 Postmaster Convention              July 1994

   addresses, and these email domains are a logical extension of the RFC
   822 Internet.  It is impossible to tell by inspecting a user's
   address whether the user receives RFC 822 mail or X.400 mail.

   Since these addresses appear to be standard RFC 822 addresses, mail
   managers, mailing list managers, host administrators, and users
   expect to be able to simply send mail to "postmaster@domain" and
   having the message be delivered to a responsible party.  When an RFC
   1327 mapping rule exists, the X.400 address element corresponding to
   the left-hand-side "postmaster" is "Surname=Postmaster" (both 1984
   and 1988).  However, neither the X.400 protocols, North America X.400
   Implementor's Agreements [7], nor the other regional X.400
   implementor's agreements require that "Surname=Postmaster" and
   "CommonName=Postmaster" be supported.  (Supporting these addresses is
   recommended in X.400 (1988)).

   For mapped X.400 domains which do not support the postmaster
   address(es), this means that an address such as ""
   might be valid, yet mail to the corresponding address
   "" fails.  This is frustrating for remote
   administrators and users, and can prevent operational problems from
   being communicated and resolved.  In this case, the desired seamless
   integration of the Internet RFC 822 mail world and the mapped X.400
   domain has not been achieved.

   The X.400 mail managers participating in the Cosine MHS Project
   discussed this problem in a meeting in June 1992 [8].  The discussion
   recognized the need for supporting the postmaster address at any
   level of the address hierarchy where these are user addresses.
   However, the group only required supporting the postmaster address
   down to certain levels of the O/R Address tree.  This approach solved
   part of the problem, but not all of it.  A more complete solution is

3.  Proposed Solution

   To fully achieve the desired seamless integration of email domains
   for which RFC 1327 mapping rules have been defined, the following
   convention must be followed,

      If there are any valid addresses of the form "user@domain", then
      the address "postmaster@domain" must also be valid.

   To express this in terms of X.400:  For every X.400 domain for which
   an RFC 1327 mapping rule exists, if any address of the form

      Surname=User; <Other X.400 Address Elements>

Cargille                                                        [Page 2]
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