IMAP Basics - What it is, and what it can do.

I've been using electronic mail for some years now, and, like many other linux users, I have more than one email address. Currently, I have about six accounts that I actively use, and several dozen other addresses that deliver to me. I used to use my email to manage my work - these days managing my email has become my work, along with managing mail for my network.

For anyone who has a requirement to access multiple separate mail accounts that reside on different machines, access to email becomes problematic. Many mail systems use the tried and tested POP3 protocol. POP3 client applications download the mail from the server, and store it on the client computer. Most clients store mail in their own format, making it inaccessible by other mail programs, and most machines which run POP3 clients are desktops, which are rarely on 24/7, further reducing access to the mail once it has been downloaded.

The IMAP protocol attempts to remedy some of these problems. The strength of IMAP lies in online and disconnected operation. Unlike POP3, mail is not copied from the server and then deleted - instead, IMAP clients manipulate the mail on the server, and permit access to remote, server hosted mailboxes as though they were local resources.

• An IMAP mail system has a number of immediate advantages for users:-
• As all mail is stored on the server, changing mail client becomes the work of seconds - all that is required is to configure a new IMAP client with the IMAP account details.
• An IMAP client can easily be configured to view multiple mailboxes in physically separate servers.
• Multiple IMAP clients can be used by each user. This makes implementing a webmail solution for roaming users a simple task.
• IMAP maintains message status flags on the server for read, answered, etc.
• IMAP allows the idea of shared folders. This makes it easier to implement generic email accounts for an organisation, and then allow multiple users to access those accounts.
• Many implementations also allow server side filtering of mail. This can be an extremely useful feature when users are accessing their mailboxes through different email clients.