Message Transfer Agent. The store-and-forward element of an email system. The end user element is a UA (User Agent). MTA and UA are terms in X.400 but are applicable to email generally, including the Internet email protocol, SMTP.
Mail Transport Agent. Unlike an MTC, the MTA actually handles sending and receiving the email to and from the system it is based upon. Most MTAs support aliasing and forwarding, as well as either the POP or IMAP protocols for clients which do not have standard MTA support upon their computer. MTAs which support POP and/or IMAP are referred to as ma... Found on http://www.nacs.uci.edu/network/network-glossary.html