SMTP (Simple Mail Transfer Protocol)

The protocol widely implemented on the Internet for exchanging email messages.

The Internet's standard host-to-host mail transport protocol. It traditionally operates over TCP, using port 25. SMTP does not provide any mailbox facility, nor any special features beyond basic mail transport.

A major standards-based protocol that allows for the transfer of messages between different messaging servers. SMTP is defined under RFC821 and uses simple command verbs to facilitate message transport over TCP/IP port 25. [Exchange 2000]

A member of the TCP/IP suite of protocols that governs the exchange of electronic mail between message transfer agents (MTA). SMTP is the default transport for Exchange Server 2003. [Exchange 2003]

A member of the TCP/IP suite of protocols that governs the exchange of electronic mail between message transfer agents. [Exchange 2007]

A protocol used by the Internet Mail Service to transfer messages between an Exchange site and an SMTP messaging system, such as the Internet. [Exchange 5.5]