What is the priority behavior of MX records?

• A. The priority decreases as the number increases.
• B. Lower mail delivery priority.
• C. Higher mail delivery priority.
• D. Mandatory TLS requirement.

Answer: (B)

MX records use a numeric value called the preference to indicate priority. The smaller the value, the higher the priority of that mail server. Mail delivery starts by trying the server with the lowest preference value; if that server can’t be reached, the next higher preference is attempted, and so on. So the behavior described is that priority decreases as the number increases: as the numeric value goes up, the server’s likelihood of being chosen goes down. This is why lower numbers are considered higher priority.

The option about lower mail delivery priority is misleading because it implies the MX record itself lowers priority, whereas the actual rule is that higher numeric values mean lower priority. The option about higher mail delivery priority would be incorrect for the same reason, and TLS requirements are unrelated to MX priority.