Simple Mail Transfer Protocol is an Internet standard for electronic mail transmission across Internet Protocol networks. SMTP was first defined by RFC 821, and last updated by RFC 5321 which includes the Extended SMTP additions, and is the protocol in widespread use today. SMTP uses TCP port 25. The protocol for new submissions is effectively the same as SMTP, but it uses port 587 instead. SMTP connections secured by SSL are known by the shorthand SMTPS, though SMTPS is not a protocol in its own right. While electronic mail servers and other mail transfer agents use SMTP to send and receive mail messages, user-level client mail applications typically use SMTP only for sending messages to a mail server for relaying. For receiving messages, client applications usually use either the Post Office Protocol or the Internet Message Access Protocol or a proprietary system to access their mail box accounts on a mail server. Wikipedia [ - ]

Simple Mail Transfer Protocol is an Internet standard for electronic mail transmission across... [ + ]