When configuring a new server, a technician requests that an MX record be created in DNS for the new server,
but the record was not entered properly. Which of the following was MOST likely installed that required an MXrecord to function properly?

A.
Load balancer

B.
FTP server

C.
Firewall DMZ

D.
Mail server

Explanation:
A mail exchanger record (MX record) is a DNS record used by email servers to determine the name of the
email server responsible for accepting email for the recipient’s domain.
For example a user sends an email to recipient@somedomain.com. The sending user’s email server will query
the somedomain.com DNS zone for an MX record for the domain. The MX record will specify the hostname of
the email server responsible for accepting email for the somedomain.com domain, for example,
mailserver.somedomain.com. The sending email server will then perform a second DNS query to resolve
mailserver.somedomain.com to an IP address. The sending mail server will then forward the email to the
destination mail server.