Ask which domain signed the solo ad

Answer A DKIM signature on a solo ad names the domain that signed the message. RFC 6376 defines that signature, including the d= tag that carries the signing domain. The question that matters before you pay is whether that domain aligns with the From address the reader sees.

The note that started this: RFC 6376, DomainKeys Identified Mail (DKIM) Signatures, RFC 6376.

The last two notes separated the author field from the envelope. The signature is the third object. A seller can show you a from-name, a platform logo, and a screenshot. None of those is the domain that signed. Ask for the domain. Then decide if the order is the send you think you are buying.

RFC 6376 is DomainKeys Identified Mail Signatures. It is not a new August rule. It is the specification a receiver uses when it checks a cryptographic signature in the message header. The signer publishes a key in DNS. The signature in the message says which domain, the d= value, is taking responsibility. If the message is altered after signing, the check fails. If a platform signs as itself while the From line says your brand, the check can succeed and still fail the alignment a mailbox uses for DMARC. Alignment is the desk question. The math can wait.

What does a DKIM signature tell you about a solo ad?

It tells you a domain claimed responsibility for the message and attached a signature a receiver can check. RFC 6376 defines that signature. It does not, by itself, prove the list wanted the mail.

Wanted mail is a list question. Did these people ask this sender for this kind of letter? A signature does not answer it. A signature answers a narrower question: which domain will stand behind this copy of the message at the moment it is checked. On a solo ad, that domain is almost always the seller's, or the seller's platform, because you do not operate the list. You are a guest in one email.

Buyers who buy solo ads sometimes receive a header dump and treat a pass as a blessing. A pass means the signature checked. It can still be a pass for a shared platform domain the reader has never heard of. It can still be a pass on mail the list did not ask for. Keep the two judgments apart. One is cryptographic. One is whether the drop belongs on that list at all.

• The signing domain is written next to the From domain.
• A recent live header, not a mock, shows the d= value.
• The seller can say who holds the DNS key.
• A mismatch is a reason to pause the order, not a reason to argue about copy.

What is the d= domain on a signed solo ad?

It is the domain named in the DKIM signature as the signing domain. The useful check is whether that domain aligns with the domain in the visible From address.

You do not need to validate the cryptography yourself. You need the string. If the From address is a brand domain and d= is the platform's mail domain, say so in the quote in plain words. Some receivers will show the reader a via line. Some will treat the mismatch as a policy failure when the brand domain publishes a DMARC record that expects alignment. The seller who cannot tell you which of those is true has not looked.

If you sell the send, sign as the domain you told the buyer you send from. A last-minute switch to a shared signer is a different product. The list may still get the mail. The buyer did not get the identity they paid to stand next to. Put the d= value in the proof you send after the drop, beside the from-name, so the order can be checked without a seminar.

What should you ask a seller about the signature before you pay?

Ask which domain will sign the live send, ask them to show the d= value from a recent message, and ask what happens to the order if the signature and the From domain do not align.

Three asks. A seller who answers with we are fully authenticated has not answered. Authenticated by whom, as which domain, on which message? The recent message matters because a test to themselves can be signed one way and the broadcast another.

Write the answer into the quote next to the refund line. The notes on safe solo ads sellers keep coming back to the same habit. Name the fact. Put it in writing. Pay after. The signature is one of the facts a mailbox will check whether you asked or not.