SIMPLE MAIL TRANSFER PROTOCOL

Domain	Definition
Computing	Simple Mail Transfer Protocol (SMTP) A protocol defined in STD 10, RFC 821, used to transfer electronic mail between computers, usually over Ethernet. It is a server to server protocol, so other protocols are used to access the messages. The SMTP dialog usually happens in the background under the control of the message transport system, e.g. sendmail but it is possible to interact with an SMTP server using telnet to connect to the normal SMTP port, 25. E.g. telnet mhs-relay.ac.uk 25 You should normally start by identifying the local host: HELO wombat.doc.ic.ac.uk You can then issue commands to verify an address or expand an alias: VRFY fred@doc.ic.ac.uk VRFY postmaster or expand a mailing list: EXPN c-help You can even send a message: MAIL From: RCPT To: DATA What is the point? . QUIT This is useful if you want to find out exactly what is happening to your message at a certain point. See also Post Office Protocol, RFC 822, sendmail. (1995-10-17). Source: The Free On-line Dictionary of Computing.
Post & Telecom	The TCP/IP standard protocol for transferring electronic mail messages from one machine to another. Source: European Union. (references)
Source: compiled by the editor from various references; see credits.

Specialty Definition: Simple Mail Transfer Protocol

Simple Mail Transfer Protocol (SMTP) is the de facto standard for email transmission across the internet.

SMTP is a relatively simple, text-based protocol, where one or more recipients of a message are specified (and in most cases verified to exist) and then the message text is transferred. It is quite easy to test a SMTP server using the telnet program. SMTP uses TCP port 25. To determine the SMTP server for a given destination, the MX (Mail eXchange) DNS record is used.

SMTP started becoming widely used in the early 1980s. At the time, it was a complement to UUCP which was better suited to handle e-mail transfers between machines that were intermittently connected. SMTP, on the other hand, works best when both the sending and receiving machines are connected to the network all the time.

Sendmail was one of the first (if not the first) mail transfer agent to implement SMTP. As of 2001 there are at least 50 programs that implement SMTP as a client (sender of messages) or a server (receiver of messages). Some other popular SMTP server programs include IBM's Postfix, D. J. Bernstein's Qmail, and Microsoft Exchange.

Since this protocol started out as purely ASCII text-based, it did not deal well with binary files. Standards such as MIME were developed to encode binary files for transfer through SMTP. Today, most SMTP servers support the 8BITMIME extension, permitting binary files to be transmitted almost as easily as plain text.

SMTP does not allow one to retrieve messages from a remote server. To do this one must use POP3 or IMAP.

SMTP security and spamming

One of the limitations of the original SMTP is that it has no facility for authentication of senders. Therefore the SMTP-AUTH extension was defined.

In spite of this, E-mail spamming is still a major problem. Modifying SMTP extensively, or replacing it completely, is not believed to be practical, due to the network effects of the huge installed base of SMTP.

For this reason, there are a number of proposals for sideband protocols that will assist SMTP operation. The Anti-Spam Research Group of the IRTF is working on a number of proposals for providing simple source authentication that is flexible, lightweight, and scalable. The most likely proposal to be accepted is the Sender Permitted From protocol.

Related RFCs

RFC2821 - The Simple Mail Transfer Protocol, which recently obsoleted RFC821
RFC1869 - Defines the capability for SMTP service extensions, creating Extended SMTP, or ESMTP
RFC1891 - Delivery Status Notification (DSN) extension to SMTP

Modern Translation: SIMPLE MAIL TRANSFER PROTOCOL

Language		Translations for "SIMPLE MAIL TRANSFER PROTOCOL"; alternative meanings/domain in parentheses.
Danish		SMTP-protokol (simple message transfer protocol, SMPT), SMTP (simple message transfer protocol, SMPT). (various references)

Dutch		SMPT (simple message transfer protocol, SMPT), simple mail transfer protocol (simple message transfer protocol, SMPT). (various references)

Finnish		SMTP (simple message transfer protocol, SMPT), simple mail transfer protocol (simple message transfer protocol, SMPT). (various references)

French		protocole SMTP (simple message transfer protocol). (various references)

German		SMTP (simple message transfer protocol, SMPT), Simple-Message-Transfer-Protocol (simple message transfer protocol, SMPT), Simple-Mail-Transfer-Protocol (simple message transfer protocol, SMPT). (various references)

Greek		SMPT (simple message transfer protocol, SMPT), πρωτόκολλο μεταφοράς απλών μηνυμάτων (simple message transfer protocol, SMPT), πρωτόκολλο μεταφοράς απλού ταχυδρομείου (simple message transfer protocol, SMPT). (various references)

Pig Latin		implesay ailmay ansfertray otocolpray

Portuguese		SMTP (simple message transfer protocol, SMPT), protocolo SMTP (simple message transfer protocol, SMPT), protocolo de transferência de correio electrónico (simple message transfer protocol, SMPT). (various references)

Spanish		protocolo simple de transferencia de correo (simple message transfer protocol, SMPT), protocolo de transferencia simple de correo (simple message transfer protocol, SMPT), protocolo de transferencia de correo electrónico (simple message transfer protocol, SMPT), protocolo de correo electrónico (simple message transfer protocol, SMPT). (various references)
Source: compiled by the editor from various translation references.

SIMPLE MAIL TRANSFER PROTOCOL

Specialty Definition: SIMPLE MAIL TRANSFER PROTOCOL

Computing

Post & Telecom

Specialty Definition: Simple Mail Transfer Protocol

SMTP security and spamming

Related RFCs

Crosswords: SIMPLE MAIL TRANSFER PROTOCOL

Modern Translation: SIMPLE MAIL TRANSFER PROTOCOL

Danish

Dutch

Finnish

French

German

Greek

Pig Latin

Portuguese

Spanish

INDEX