What is a Mail eXchange or Email mail delivery agent (MDA | LDA)?


A mail delivery agent (MDA) or Mail eXchange 1) is a SMTP server that is responsible for the local delivery (reception) of e-mail messages to a mailbox

It's also known as:

  • message delivery agent (MDA)
  • local delivery agent (LDA)
  • Mail eXchange (MX)

An MDA gets normally the messages from an MTA (Smtp Server) and delivers them to a mailbox (real or virtual).

Mx record

The email servers IP are set in the DNS via the MX record. This is how a server knows to which server a message should be sent.

For instance, with the email address [email protected], the MTA server will:


The submission port is the port 25.


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