X.400 has Message Store, Internet Mail has IMAP and POP

The P7 Message Store

X.400 (1988) defines the concept of a "message store": a place where the user can have messages delivered for pickup at a later time.

The X.400 message store is defined in X.411 and X.413; it defined (in 1988) a message store where the user could get some information about incoming messages, and fetch and delete messages selectively.

Status information on the message indicates whether it was read or not; functionality exists to make the message store send a Receipt Notification when the message status changes to "read".

In later versions, I believe functionality was added to let the user add "keywords" to the message, forming the basis for a "folder" facility, and to store information about outgoing messages.

The protocol used to access the message store is called "P7". It has numerous options, among others what parts of the message it is possible to access separately, and functions that need not be implemented.

It is used in, among others, the Maxware User Agent and the Nexor "XUA".

Internet POP

The simplest Internet mailbox protocol is the Post Office Protocol, POP, which allows the user to list, retrieve and delete messages.

The intention of the POP protocol is to form an effective spool file access mechanism for PCs so that the user does not have to log in to the mailbox system.

Simple authorization based on passwords, with optional password hiding using MD5, is available.

Message submission is done using SMTP, not POP.

The protocol is in numerous products including the popular EUDORA mailer for PCs.

The IMAP protocol

A more ambitious protocol is IMAP, currently in its fourth incarnation. This provides the user with functions to manage a set of "folders", with access functions allowing the retrieval and listing of parts of a MIME message, read-only folders and so on.

One intention of the newest version was to allow "disconnected operation", where a "main mailbox" would reside on a server, and a client on a portable would carry the "current mailbox", with easy synchronization between the two when they are connected, merging updates done in both mailboxes.

Several security functions, including encrypted connections, are defined.

The protocol forms the basis of products such as PINE.

A comparision

The X.400 P7 Message Store is somewhat more powerful than POP. With the addition of "keywords", it may be very similar to IMAP in functionality. It uses ASN.1 and Remote Operations, being thus able to use security functions defined in an OSI context. (Some people will argue over whether this is an advantage or disadvantage)

IMAP uses a character-based encoding of its protocol.

Last modified: Fri Aug 11 14:42:13 1995