What is IMAP?

IMAP, or Internet Message Access Protocol, formerly known as the Interactive Mail Access Protocol, is a protocol that enables e-mail clients to retrieve e-mail messages from a mail server, and work with the mailboxes on a mail server. IMAP is the protocol that IMAP clients use to communicate with the servers. SMTP is the protocol used to transport mail to an IMAP server.

IMAP4, the latest version, is similar to POP3 but offers additional and more complex features. For example, the IMAP4 protocol leaves your e-mail messages on the server rather than downloading them to your computer. If you wish to remove your messages from the server, you must use your mail client to generate local folders, copy messages to your local hard drive, and then delete and expunge the messages from the server.

IMAP was developed at Stanford University in 1986.