The Mail Delivery Agent reference article from the English Wikipedia on 24-Jul-2004
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Mail Delivery Agent

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A Mail Delivery Agent (MDA) is software that accepts incoming e-mail messages and distributes them to recipients' individual mailboxes (if the destination account is on the local machine), or forwards back to an SMTP server (if the destination is on a remote server).

A mail delivery agent is not necessarily a mail transfer agent (MTA).