The Mail Transfer Agent (MTA) is primarily responsible for moving messages between connectors. The MTA moves messages from inbound queues to the respective outgoing queues of different connectors based on rules defined in an Address Map table.

Examples of MTA functionality follow:

• Receiving inbound messages from mail connectors
• Delivering mail to local mailboxes
• Queueing mail for relay to other mail connectors (including themselves, as in SMTP Relay)
• Executing external filters (such as antivirus) and pickup events
• Archiving messages