MAIL TRANSFER AGENT

A 'mail transfer agent' or 'MTA' (also called a 'mail transport agent', 'message transfer agent', 'mail server', or a 'mail exchanger' in the context of the Domain Name System) is a computer program or software agent that transfers electronic mail messages from one computer to another.
It receives messages from another MTA (relaying), a mail submission agent (MSA) that itself got the mail from a mail user agent (MUA), or directly from an MUA, thus acting as an MSA itself. The MTA works behind the scenes, while the user usually interacts with the MUA.
The delivery of e-mail to a user's mailbox typically takes place via a mail delivery agent (MDA); many MTAs have basic MDA functionality built in, but a dedicated MDA like procmail can provide more sophistication.
According to various surveys
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the most popular mail server software are Sendmail, Postfix, Microsoft Exchange Server, Exim, IMail (by Ipswitch, Inc.), MDaemon by Alt-N Technologies, MailEnable, Merak Mail Server and qmail.
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Many organizations use the services of e-mail security services such as Postini, MXLogic or Concentric Hosting to receive e-mail.

Contents

See also

Mail server surveys

See also

★ MX record

★ List of mail servers

★ Comparison of mail servers

★ Mail delivery agent
mail transfer agent

Mail server surveys

1. Security Space Mail (MX) Server Survey, 1st Aug 2007.
2. MailChannels.com Mail Server Survey, 2006
3. ''Anonymous'', Open source Mail Server Comparison, November 2003
4. Daniel J. Bernstein, Internet host SMTP server survey, November 2001
5. Dan Shearer, MTA Comparison, January 2007