A few weeks after deploying additional email servers, employees complain that messages are being marked...

SPF (Sender Policy Framework) DNS records specify which mail servers are authorized to send email on behalf of a domain. When new email servers are added but SPF records are not updated, recipient mail systems cannot verify the legitimacy of the new servers. As a result, those messages are flagged as spam or rejected altogether.

CompTIA Security+ SY0-701 highlights SPF as an essential email authentication mechanism used to reduce spoofing, phishing, and spam classification errors. Updating the SPF record to include the new servers ensures email reputation is maintained and messages are delivered properly.

CNAME (A) maps hostnames but does not affect outbound email legitimacy. SMTP (B) is the mail protocol, not the authentication method. DLP (C) governs sensitive data handling, not spam classification.

Thus, SPF is the correct answer.