(MTA, Mail Transport Agent) The program responsible for delivering e-mail messages. Upon receiving a message from a Mail User Agent or another MTA it stores it temporarily locally and analyses the recipients and either delivers it (local addressee) or forwards it to another MTA (routing). In either case it may edit and/or add to the message headers. The most widely used MTA for Unix is sendmail, which communicates using SMTP. [Other OSes?] (1997-02-28)
