Summary: POP3 has become the most common email client connection protocol.

Your email client talks to your email server to send it commands to login, get mail status, and send and receive email. The most common protocol used by email clients to communicate with email servers is the Post Office Protocol.

The POP3 protocol enables any email program anywhere on the Internet to connect to any email server to perform the usual email functions, such as reading and sending, as long as they have a valid account and password.

The POP3 protocol does not support multi-mailbox accounts. If a client application specifies a multi-mailbox (folder) account, the INBOX mailbox is opened.

When the client application sends a request to delete a message from the mailbox,the message is not deleted immediately, but it is marked by the server. Only when the client application ends the session properly and closes the connection, the marked messages are then removed.

The Internet Message Access Protocol (IMAP) is a more modern protocol than POP3, and was first developed at Stanford University in 1986. The current version is IMAP4,and provides similar services to the POP3 protocol, but includes additional features such as the ability to keep your email on the server after downloading a copy to read locally.

The IMAP features can be useful in several situations, for example when you are traveling and don't want to download your email onto a laptop, because then you won't have them on your home computer. It can also be useful for use on low-bandwidth devices like personal digital assistants, enabling you to select a few email from a list of subject headers before downloading just the ones you want.