Mail transfer agent

A mail transfer agent or MTA is a software computer program which transfers electronic mail messages from one computer to another. The MTA works behind the scenes, while the user usually interacts with another program, the mail user agent, which contacts an MTA for actual delivery of the mail.

One of the most popular MTAs is sendmail, which implements the standard SMTP mail transfer protocol. The Microsoft Exchange[?] server contains an MTA as well. Others include Qmail.

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