SMTP
Simple Mail Transfer Protocol. The standard e-mail protocol on the Internet.
SMTP was originally designed for text, but MIME and other encoding methods enable program and multimedia files to be attached
to e-mail messages.
SMTP servers route SMTP messages throughout the Internet to a mail server,
such as POP3 or IMAP4, which provides a message store for incoming mail.
A protocol used to transfer electronic mail between computers. It is specified
in RFC 821, with extensions specified in many other RFCs. It is a server to
server protocol, so other protocols are used to access the messages. See also:
Electronic Mail, Post Office Protocol, RFC 822.