What is a Mail eXchange (or MX)?

About

A Mail eXchange (MX) is a smtp server that is responsible for :

• receiving emails for one or more domain
• and delivering them to a mail delivery agent (MDA) for final delivery

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:

• lookup the MX record for the domain name yolo.bar.com,
• connect to the corresponding email server on the port 25
• and transmit the message

Port

The reception port is the port 25.

List

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