What does POP3 stand for?

POP3 stands for Post Office Protocol 3. It is an application-layer protocol used by an email client to retrieve messages from a mail server, traditionally downloading them to the user’s device.

The “3” identifies the third major version of the protocol. POP3 is intentionally simple: a client connects, authenticates, lists or downloads messages, and can usually delete them from the server. This design suited an era when people commonly read email from one primary computer and had limited storage or network access.

POP3 is often confused with SMTP and IMAP. SMTP, or Simple Mail Transfer Protocol, is used primarily to send and relay email. IMAP, or Internet Message Access Protocol, keeps messages and folders synchronized on the server, making it better for people who use several devices. POP3 can still be useful for archival or single-device workflows, but modern email services frequently favor IMAP or webmail for synchronization.

Secure email connections commonly wrap POP3 in TLS, often using port 995, while traditional unencrypted POP3 uses port 110.