Tom has been told that the DNS MX record has been changed. What does this record pertain to?

A.
Mail transfer agent

B.
Mail agent

C.
Multiplexor exchanger

D.
Mail exchanger

Explanation:
The term mail server is also loosely used to mean a computer acting as
an Mail transfer agent by running the appropriate software. The term mail exchanger
(MX), in the context of the Domain Name System formally refers to an IP address
assigned to a device hosting a mail server, and by extension also indicates the
server itself.