What is IMAP or POP3 and how does it work?

POP stands for 'Post Office Protocol 3', a standard protocol for receiving email.

A POP3 mail server receives the email addressed to you and, when you log in to this server, forwards it to you. The email is then physically removed from the mail server and actually ends up on your own computer.

The counterpart of this protocol is IMAP ('Interactive Mail Access Protocol'). With IMAP, the mail stays on the email server until you decide to delete the message from the server yourself.

You view/read IMAP mail either via webmail or via an email program that supports IMAP.

Webmail speaks for itself, but we can tell you a bit more about IMAP in, for example, Outlook Express.

When adding an account to Outlook Express (or another email program), you can specify whether it is POP or IMAP mail (usually found under extended options/advanced, and can only be chosen when CREATING an account).

The email client will then start synchronising. It makes a copy of every email/folder that is also on the mail server. If you look via webmail, you will see the same emails/folders as via IMAP.

If you use IMAP in combination with POP3, things get a little more complex because they actually work against each other (unless you specify in POP3 that a copy of the mail should be kept on the server). If you collect mail with POP3 and then look with IMAP, no messages will be visible.