A museum wants other mail servers to know which hosts are allowed to send mail for its domain. Which DNS record publishes that policy?
Select an answer to reveal the explanation.
Short Explanation
The museum needs a note that says who is allowed to send, not a sign that says where incoming mail should be delivered. You publish that note as a TXT record with an SPF policy. A mail-exchanger record, an IPv6 address, and a DHCP reservation do not list the allowed senders.
Full Explanation
SPF is a sender policy, and it is published in a TXT record so other servers can see which hosts may send mail for the domain. An MX record names where incoming mail should be delivered. It does not list who may send. An AAAA record stores an IPv6 address. It is not a sender policy. A DHCP reservation ties a MAC address to an IP address. It is not a DNS policy and it does not publish a sender list. Exam caveat: the hosts that send mail still need to be the ones named in the policy. A correct TXT record does not help if a new mail host was left out of it. Operational check: query the domain's TXT records, confirm the SPF policy names the museum's sending hosts, and send a test message from one of them. Send a test message from a host the policy names and confirm it is accepted. Note the result on the ticket. Leave a new sending host out of the policy only if it should not send.