IMAP is an acronym for Internet Message Access Procotol.
As its name implies, IMAP is a protocol for accessing email messages. This differs from POP3, which is primarily a protocol for transferring (or moving) messages.
When IMAP is used by email programs to access messages stored on an email server, they are left on that server unless explicitly deleted or moved by the user. Copies of email messages may be downloaded, but fundamentally, IMAP provides what can best be termed a window or a view on a collection of email stored on the server.
While copies of email may be downloaded, enabling offline access, the IMAP protocol works best when continuously connected to the email server. Changes on that server – such as new mail arriving, or email being deleted or altered by a web interface or another email program – are quickly reflected in programs accessing that email server via IMAP.
Multiple-simultaneous access – meaning more than one computer or device accessing the same collection of email at the same time – is one of IMAP’s strengths, and it’s often the technology used by mobile devices, and even web interfaces, to manage email that might be accessed from multiple locations. The down side is the more or less constant connection that’s best used, as well as the fact that email accumulates on the email server unless deleted, which can sometimes cause email accounts to exceed storage quotas.
For more, see What is IMAP? And how can it help me manage my email? on Ask Leo!.« Back to Glossary Index