Proofpoint TPAD01 Exam - Topic 13 Question 18 Discussion

The correct answer is DKIM Signature because DKIM works by adding a cryptographic signature into the message headers. That header contains information such as the signing domain and a selector, and the signature is generated from selected parts of the message, including specific headers and sometimes the body hash. Proofpoint's DKIM reference explains that the ''s='' value in the DKIM-Signature header is the selector, which is used to locate the correct public key in DNS for signature validation. This is the exact clue that matches the question wording about a selector being included in the header.

The other choices do not fit what the question describes. SPF is a DNS-based sender authorization check and is not inserted as a cryptographic signature header in the message. DMARC is a policy framework that tells receivers how to treat mail that fails SPF or DKIM alignment, and ARC is used to preserve authentication assessment across forwarding chains rather than being the core sender signature described here. In the Proofpoint administrator context, DKIM is one of the key email authentication controls because it helps prove message integrity and domain-associated signing. So when the course asks which item adds a header containing a selector and a hash-based signature over selected header values, that is the DKIM Signature.