Main Page | See live article | Alphabetical index A Mail Delivery Agent (MDA) is software that accepts incoming 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 (MDA) is NOT necsessarily a Mail Transfer Agent (MTA). Tools like procmail are called Mail Delivery Agents, but they do not support the SMTP protocol, and can therefore not be called Mail Transfer Agents This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.