MTA

MTA is an acronym for Mail Transport Agent. It is the software that works behind the scenes to transport E-Mail messages from one computer to another.

MUAs (such as Thunderbird, Outlook, Apple Mail, etc.) hand off newly sent messages to an MTA. MTAs talk to other MTAs, and either deliver mail locally or hand it off for delivery to a MDA.

MTA is a generic term and usually refers to one of these popular software packages:

• Postfix flexible mailer.
• Exim
• Sendmail, the original BSD mailer.
• Courier
• qmail is an obsolete and unmaintained server. If you really intend to continue using it, read Dave Sill's Life with qmail which contains instructions to work around some of qmail's security issues.
• HALON is a commercial MTA, which supports Dovecot Auth and LMTP.

Some people also subsume mail fetching utilities under the MTA category, among them:

• fetchmail, a fast mail retriever.
• getmail,a mail retrieval utility written in Python.

These mail fetching utilities can be used to store mail for later retrieval by Dovecot.