RFC 1176 (rfc1176) - Page 2 of 30
Interactive Mail Access Protocol: Version 2
Alternative Format: Original Text Document
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 satisfactory today unless the concept of a host is changed to refer to an organizational entity and not a particular machine. (5) It is difficult to keep a multitude of heterogeneous machines Crispin
