Post Office Protocol — Version 3
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J. Myers, M. Rose · 1996-05
Abstract
The Post Office Protocol version 3 (POP3) defines a protocol for email clients to retrieve messages from a remote mail server. POP3 operates over TCP port 110 (or 995 with TLS) and provides commands for authentication, listing, retrieving, and deleting messages. Its design assumes that messages are downloaded to the client and typically deleted from the server.
Why This RFC Matters
POP3 brought email access to millions of users with dial-up Internet connections in the 1990s, enabling offline reading of downloaded messages. Its simplicity made implementation straightforward for both servers and clients. While largely supplanted by IMAP (RFC 3501) for modern multi-device email workflows — since IMAP keeps messages server-side — POP3 remains in use in environments with limited server storage or where permanent local archival is required. RFC 1939 superseded RFC 1225.