Intermail and Commercial Mail Relay services
RFC 1168

Document Type RFC - Informational (July 1990; No errata)
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Network Working Group                                         A. Westine
Request for Comments: 1168                                    A. DeSchon
                                                               J. Postel
                                                               C.E. Ward
                                                                 USC/ISI
                                                               July 1990

              INTERMAIL AND COMMERCIAL MAIL RELAY SERVICES

STATUS OF THIS MEMO

   This RFC discusses the history and evolution of the Intermail and
   Commercial mail systems.  The problems encountered in operating a
   store-and-forward mail relay between commercial systems such as
   Telemail, MCI Mail and Dialcom are also discussed. This RFC provides
   information for the Internet community, and does not specify any
   standard.  Distribution of this memo is unlimited.

INTRODUCTION

   The evolution of large electronic mail systems testifies to the
   increasing importance of electronic mail as a means of communication
   and coordination throughout the scientific research community.

   This paper is a summary of the development of, and a status report
   on, an experiment in protocol interoperation between mail systems of
   different design. USC/Information Sciences Institute (ISI) began work
   on this experiment in 1981 and over the years has provided an
   evolving demonstration service for users to exchange mail between the
   Internet and a few commercial mail systems.

   Recently other organizations have begun to provide similar services,
   demonstrating the ongoing need for interoperation of the Internet and
   the commercial mail systems.  We believe that ISI's pioneering work
   in this area has promoted this expansion of service.

   These systems include the Internet mail system, the US Sprint
   Telemail system, the MCI Mail system, and the Dialcom systems. All of
   the systems were designed to operate autonomously, with no convenient
   mechanism to allow users of one system to send electronic mail to
   users on another system.

   The Intermail and Commercial Mail Relay (CMR) services described in
   this paper were developed to provide a means for sending mail between
   the Internet and these commercial mail systems.

Westine, DeSchon, Postel & Ward                                 [Page 1]
RFC 1168      Intermail and Commercial Mail Relay Services     July 1990

   The Internet is an interconnected system of networks using the SMTP
   mail protocol, which includes the ARPANET, MILNET, NSFNET, and about
   700 other networks; mail relays allow the exchange of mail with
   BITNET, CSNET, and the UUCP networks as well.  To the users, this
   Internet looks like one large mail system with at least 100,000
   computers and at least 400,000 users.  Figure 1 illustrates the path
   of a message sent by a user on one Internet host to a user on another
   Internet host.  For more details on the Internet and connected
   networks (see Appendix A).

   As commercial mail systems came into popular use, it became clear
   that a mail link between the Internet and the commercial mail systems
   was necessary (see Appendix B).  More and more commercial and
   research entities needed to communicate with the Internet research
   community, and many of these organizations (for one reason or
   another) were inappropriate candidates for Internet sites.  The
   Intermail and CMR services allow these groups to communicate with
   Internet users by purchasing electronic mail services from commercial
   companies.

INTERMAIL

   Intermail is an experimental mail forwarding system that allows users
   to send electronic mail across mail system boundaries. The use of
   Intermail is nearly transparent, in that users on each system are
   able to use their usual mail programs to prepare, send, and receive
   messages.  No modifications to any of the mail programs on any of the
   systems are required.  However, users must put some extra addressing
   information at the beginning of the body of their messages.

               <<< Figure 1 - Internet to Internet Mail >>>

   The earliest version of Intermail was developed in 1981, by Jon
   Postel, Danny Cohen, Lee Richardson, and Joel Goldberg [1]. It ran on
   the TOPS-20 operating system and was used to forward VLSI chip
   specifications for the MOSIS project between the ARPANET and the
   Telemail system.  The original addressing model used in this system
   was called "Source Route Forwarding".  It was developed to handle
   situations in which a message might travel multiple hops before
   reaching its destination.

   Later, in 1983, Annette DeSchon converted Intermail into a more
   general-purpose mail-forwarding system, supporting forwarding between
   the Internet mail system and three commercial mail systems: Telemail,
   MCI Mail, and Dialcom [3,4].

Westine, DeSchon, Postel & Ward                                 [Page 2]
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