Interactive Mail Access Protocol: Version 2
RFC 1176
Document | Type |
RFC - Experimental
(August 1990; No errata)
Obsoletes RFC 1064
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Author | Mark Crispin | ||
Last updated | 2013-03-02 | ||
Stream | Legacy | ||
Formats | plain text html pdf htmlized bibtex | ||
Stream | Legacy state | (None) | |
Consensus Boilerplate | Unknown | ||
RFC Editor Note | (None) | ||
IESG | IESG state | RFC 1176 (Experimental) | |
Telechat date | |||
Responsible AD | (None) | ||
Send notices to | (None) |
Network Working Group M. Crispin Request for Comments: 1176 Washington Obsoletes: RFC 1064 August 1990 INTERACTIVE MAIL ACCESS PROTOCOL - VERSION 2 Status of this Memo This RFC suggests a method for personal computers and workstations to dynamically access mail from a mailbox server ("repository"). It obosoletes RFC 1064. This RFC specifies an Experimental Protocol for the Internet community. Discussion and suggestions for improvement are requested. Please refer to the current edition of the "IAB Official Protocol Standards" for the standardization state and status of this protocol. Distribution of this memo is unlimited. Introduction The intent of the Interactive Mail Access Protocol, Version 2 (IMAP2) is to allow a workstation, personal computer, or similar small machine to access electronic mail from a mailbox server. Since the distinction between personal computers and workstations is blurring over time, it is desirable to have a single solution that addresses the need in a general fashion. IMAP2 is the "glue" of a distributed electronic mail system consisting of a family of client and server implementations on a wide variety of platforms, from small single- tasking personal computing engines to complex multi-user timesharing systems. Although different in many ways from the Post Office Protocols (POP2 and POP3, hereafter referred to collectively as "POP") described in RFC 937 and RFC 1081, IMAP2 may be thought of as a functional superset of these. RFC 937 was used as a model for this RFC. There was a cognizant reason for this; POP deals with a similar problem, albeit with a less comprehensive solution, and it was desirable to offer a basis for comparison. Like POP, IMAP2 specifies a means of accessing stored mail and not of posting mail; this function is handled by a mail transfer protocol such as SMTP (RFC 821). This protocol assumes a reliable data stream such as provided by TCP or any similar protocol. When TCP is used, the IMAP2 server listens on port 143. Crispin [Page 1] RFC 1176 IMAP2 August 1990 System Model and Philosophy Electronic mail is a primary means of communication for the widely spread Internet community. The advent of distributed personal computers and workstations has forced a significant rethinking of the mechanisms employed to manage electronic mail. With mainframes, each user tends to receive and process mail at the computer he uses most of the time, his "primary host". The first inclination of many users when an independent workstation is placed in front of them is to begin receiving mail at the workstation, and many vendors have implemented facilities to do this. However, this approach has several disadvantages: (1) Personal computers and many workstations have a software design that gives full control of all aspects of the system to the user at the console. As a result, background tasks such as receiving mail may not run for long periods of time; either because the user is asking to use all the machine's resources, or because the user has (perhaps accidentally) manipulated the environment in such a way that it prevents mail reception. In many personal computers, the operating system is single-tasking and this is the only mode of operation. Any of these conditions could lead to repeated failed delivery attempts by outside agents. (2) The hardware failure of a single machine can keep its user "off the air" for a considerable time, since repair of individual units may be delayed. Given the growing number of personal computers and workstations spread throughout office environments, quick repair of such systems is not assured. On the other hand, a central mainframe is generally repaired soon after failure. (3) Personal computers and workstations are often not backed up with as much diligence as a central mainframe, if at all. (4) It is more difficult to keep track of mailing addresses when each person is associated with a distinct machine. Consider the difficulty in keeping track of many postal addresses or phone numbers, particularly if there was no single address or phone number for an organization through which you could reach any person in that organization. Traditionally, electronic mail on the ARPANET involved remembering a name and one of several "hosts" (machines) whose name reflected the organization in which the individual worked. This was suitable at a time when most organizations had only one central host. It is less satisfactoryShow full document text