message delivery agent (MDA)

A Mail Delivery Agent(MDA) or Message Delivery Agent is an e-mail client in an e-mail system.

Mail communication over the Internet

The Message Delivery Agent has delivery functions that the Mail Transfer Agent( MTA) uses to deposit messages in Mail User Agent( MUA) mailboxes.

The mail client creates, receives, and reads the messages and transfers them over the Internet using Simple Mail Transfer Protocol( SMTP). The messages from the Mail User Agent (MUA) are transmitted using Post Office Protocol( POP) or Internet Message Access Protocol( IMAP) and forwarded by the MDA agent to the Mail Transfer Agent (MTA). On the receiving side, the MDA agent delivers the e-mails to the local system.