Understanding the IMAP4 Protocol

Overview

Internet Message Access Protocol version 4 (IMAP4) is an Internet messaging protocol that enables a client to access mail on a server rather than downloading it to the user's computer. IMAP4 is designed for an environment in which a user logs on to the server from several different workstations. In such an environment, downloading a user's mail to a specific computer is usually impractical because the user does not always use the same computer. For example, IMAP4 is widely used in universities where students connect to the mail server from different labs throughout the campus. Once connected, users can access their mailboxes as though their mail is stored locally. IMAP4 does not handle sending mail; this functionality is handled by Simple Mail Transfer Protocol (SMTP).

Comparisons with POP3

Post Office Protocol version 3 (POP3) also allows clients to access mail on the server; however, it is designed primarily for offline use. POP3 enables users to connect to the server and download all of their mail to the client. Unlike IMAP4 users, POP3 users cannot access mail in public folders on the server. POP3 clients can only access mail in their Inboxes.

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