Post Office Protocol

In computing, the Post Office Protocol version 3 (POP3) is an  application-layer Internet standard  protocol used by local e-mail clients to get e-mail from a remote mail server over a TCP/IP connection.  POP3 and IMAP4 (Internet Message Access Protocol) are the two most widely accepted Internet standard protocols for e-mail retrieval.  Almost all modern e-mail clients and servers support both.

Many years ago, a proposal was outlined for a POP4 specification, complete with a working server implementation.  The proposed POP4 extension adds basic folder management, multipart message support, as well as message flag management, allowing for a light protocol which supports some popular IMAP features which POP3 lacks.  No progress has been found in the POP4 specification since 2003.

 Related Requests For Comments (RFCs) 
 RFC 1939 – Post Office Protocol - Version 3 (STD 53)
 RFC 1957 – Some Observations on Implementations of the Post Office Protocol (POP3)
 RFC 2195 – IMAP/POP AUTHorize Extension for Simple Challenge/Response
 RFC 2384 – POP URL Scheme
 RFC 2449 – POP3 Extension Mechanism
 RFC 2595 – Using TLS with IMAP, POP3 and ACAP
 RFC 3206 – The SYS and AUTH POP Response Codes
 RFC 5034 – The Post Office Protocol (POP3) Simple Authentication and Security Layer (SASL) Authentication Mechanism

Related pages
 Internet Message Access Protocol (IMAP)
 Simple Mail Transfer Protocol (SMTP)
 E-mail client
 Webmail
 POP3 clients: getmail, fetchmail
 Email encryption

Category:Computer protocols
Category:E-mail