Simple Mail Transfer Protocol.
Short for Simple Mail Transfer Protocol. A protocol used on TCP/IP networks governing the transfer of e-mail.
(Simple Mail Transfer Protocol) The standard email protocol on the Internet and part of the TCP/IP protocol suite, as defined by IETF RFC 2821. SMTP defines the message format and the message transfer agent (MTA), which stores and forwards the mail. SMTP was originally designed for only plain text (ASCII text), but MIME and other encoding methods enable executable programs and multimedia files to be attached to and transported with the email message.SMTP servers route SMTP messages throughout the Internet to a mail server that provides a message store for incoming mail. The mail server uses the POP3 or IMAP4 access protocol to communicate with the user's email program. See POP3, IMAP4, MIME and messaging system. See also SNMP.
An Application Layer protocol of the TCP/IP protocol suite, SMTP was defined by the IETF in RFC 821 (1982) for passing e-mail to and through the Internet between clients and servers. SMTP operates over the connectionless User Datagram Protocol (UDP) and supports text-oriented e-mail between any two devices that support Message Handling Service (MHS). SMTP was developed to support the 7-bit ASCII code, which accommodates plain text, including letters, numbers, punctuation marks, and a reasonable set of control characters. ASCII, however, does not support the rich text formatting (e.g., italics, bold, and color, other than the default black in which this document is printed) supported by most contemporary word processing programs.This 7-bit format also prevents the transmission of 8-bit binary data found in executable files. The Multipurpose Internet Mail Extensions (MIME) to SMTP are used to support binary files, and Secure MIME (S/MIME) supports encryption. See also Application Layer, ASCII, binary, client/server, connectionless, e-mail, IETF, Internet, MHS, MIME, plain text, POP3, protocol suite, RFC, rich text, S/MIME, TCP/IP, and UDP.