Mapping between X.400 and RFC 822
RFC 987

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UCL Technical Report 120
Mailgroup Note 19

Network Working Group                                         S.E. Kille
Request for Comments: 987                      University College London
                                                               June 1986

                   Mapping between X.400 and RFC 822

Status of This Memo

   This RFC suggests a proposed protocol for the ARPA-Internet
   community, and requests discussion and suggestions for improvements.
   Distribution of this memo is unlimited.

   This document describes a set of mappings which will enable
   interworking between systems operating the CCITT X.400 (1984) series
   of protocols [CCITT84a], and systems using the RFC 822 mail protocol
   [Crocker82a], or protocols derived from RFC 822.  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 specification should be used when this mapping is performed on
   the ARPA-Internet or in the UK Academic Community.  This
   specification may be modified in the light of implementation
   experience, but no substantial changes are expected.

Kille                                                           [Page 1]



RFC 987                                                        June 1986
Mapping between X.400 and RFC 822

Chapter 1 -- Overview

   1.1.  X.400

      The X.400 series protocols have been defined by CCITT to provide
      an Interpersonal Messaging Service (IPMS), making use of a store
      and forward Message Transfer Service.  It is expected that this
      standard will be implemented very widely.  As well as the base
      standard (X.400), work is underway on various functional standards
      of profiles which specify how X.400 will be used in various
      communities.  Many of the major functional standards (e.g. from
      CEPT, CEN/CENELEC, and NBS) are likely to be similar.  Some of the
      decisions in this document are in the light of this work.  No
      reference is given, as these documents are not currently stable.

   1.2.  RFC 822

      RFC 822 evolved as a messaging standard on the DARPA (the US
      Defense Advanced Research Projects Agency) Internet.  It is
      currently used on the ARPA-Internet in conjunction with two other
      standards: RFC 821, also known as Simple Mail Transfer Protocol
      (SMTP) [Postel82a], and RFC 920 which is a specification for a
      domain name system and a distributed name service [Postel84a].
      RFC 822, or protocols derived from RFC 822 are used in a number of
      other networks.  In particular:

         UUCP Networks

            UUCP is the UNIX to UNIX CoPy protocol <0>, which is usually
            used over dialup telephone networks to provide a simple
            message transfer mechanism.  There are some extensions to
            RFC 822, particularly in the addressing.  They are likely to
            use domains which conform to RFC 920, but not the
            corresponding domain nameservers [Horton86a].

         CSNET

            Some portions of CSNET will follow the ARPA-Internet
            protocols. The dialup portion of CSNET uses the Phonenet
            protocols as a replacement for RFC 821.  This portion is
            likely to use domains which conform to RFC 920, but not the
            corresponding domain nameservers.

         BITNET

            Some parts of BITNET use RFC 822 related protocols, with
            EBCDIC encoding.

Kille                                                           [Page 2]



RFC 987                                                        June 1986
Mapping between X.400 and RFC 822

         JNT Mail Networks

            A number of X.25 networks, particularly those associated
            with the UK Academic Community, use the JNT (Joint Network
            Team) Mail Protocol, also known as Greybook [Kille84a].
            This is used with domains and name service specified by the
            JNT NRS (Name Registration Scheme) [Larmouth83a].

      The mappings specified here are appropriate for all of these
      networks.

   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 X.400 systems.  This
      will be a requirement, even in cases where communities intend to
      make a transition to use of X.400, where conversion will be needed
      to ensure a smooth service transition.  It is expected that there
      will be more than one gateway <1>, and this specification will
      enable them to behave in a consistent manner.  These gateways are
      sometimes called mail relays.  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.