Definition: POP3

(Post Office Protocol 3) A programming interface (API) from the IETF that enables a user's email program to access the mail server (RFC 1939 standard). Email clients such as Outlook, Mail, Eudora and Thunderbird are typically configured to retrieve mail either via POP3 or IMAP4, the other popular standard.

POP3 is a simple system with limited selectivity. Incoming messages and attachments are downloaded when users check their mail, and POP is typically configured to delete the messages on the server after downloading. If the user opts to not delete them, the messages will download again the next time mail is checked. See IMAP4, email interfaces, SMTP and messaging system.

Incoming Mail Options

Most Internet mail services offer all three options. Users may choose IMAP if they need access from several computers or if they like to keep mail online indefinitely (see IMAP4).