RFC 984 (rfc984) - Page 1 of 31

PCMAIL: A distributed mail system for personal computers

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Network Working Group                                     David D. Clark
Request for Comments: 984                                Mark L. Lambert
                                M. I. T. Laboratory for Computer Science
                                                                May 1986

        PCMAIL: A Distributed Mail System for Personal Computers


1. Status of this Document

   This document is a preliminary discussion of the design of a
   personal-computer-based distributed mail system.  It is published for
   discussion and comment, and does not constitute a standard.  As the
   proposal may change, implementation of this document is not advised.
   Distribution of this memo is unlimited.

2. Introduction

   Pcmail is a distributed mail system that provides mail service to an
   arbitrary number of users, each of which owns one or more personal
   computers (PCs).  The system is divided into two halves.  The first
   consists of a single entity called the "repository".  The repository
   is a storage center for incoming mail.  Mail for a Pcmail user can
   arrive externally from the Internet or internally from other
   repository users.  The repository also maintains a stable copy of
   each user's mail state (this will hereafter be referred to as the
   user's "global mail state").  The repository is therefore typically a
   computer with a large amount of disk storage.

   The second half of Pcmail consists of one or more "clients". Each
   Pcmail user may have an arbitrary number of clients, which are
   typically PCs.  The clients provide a user with a friendly means of
   accessing the user's global mail state over a network. In order to
   make the interaction between the repository and a user's clients more
   efficient, each client maintains a local copy of its user's global
   mail state, called the "local mail state". Since clients are PCs,
   they may not always have access to a network (and therefore to the
   global mail state in the repository).  This means that the local and
   global mail states may not be identical all the time, making
   synchronization between local and global mail states necessary.

   Clients communicate with the repository via the Distributed Mail
   System Protocol (DMSP); the specification for this protocol appears
   in appendix A. The repository is therefore a DMSP server in addition
   to a mail end-site and storage facility.  DMSP provides a complete
   set of mail manipulation operations ("send a message", "delete a
   message", "print a message", etc.).  DMSP also provides special
   operations to allow easy synchronization between a user's global mail
   state and his clients' local mail states.  Particular attention has
   been paid to the way in which DMSP operations act on a user's mail
   state.  All DMSP operations are atomic (that is, they are guaranteed


Clark & Lambert
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