Look up and validate DKIM DNS records for email domain authentication. Verify selector, key type, and key data.
A DKIM check starts with two identifiers: the sending domain and the selector named in an email's DKIM-Signature header. This tool combines them into the DNS name selector._domainkey.domain, retrieves its TXT record, and examines the DKIM tags, including the key type and public-key data. The selector is the frequent source of confusion. It is chosen by the sender and is not necessarily "default," the mail provider's name, or the domain itself. A record can also validate structurally without proving that current messages are being signed correctly.
The lookup name is formed by placing the selector before _domainkey and the signing domain. For selector mail2026 and domain example.com, the resulting owner name is mail2026._domainkey.example.com. The checker requests TXT data at that exact name. A record published under another selector, subdomain, or organizational domain will not satisfy this lookup.
A retrieved DKIM record is interpreted as a semicolon-separated tag list. The v= tag identifies the DKIM version, k= identifies the public-key type when present, and p= carries the encoded public-key data. The checker reports whether the expected record and usable key data are present. It does not possess the corresponding private key and cannot test signing by itself.
Open the headers of a message sent by the system you are checking and locate its DKIM-Signature field. The value following s= is the selector, while d= is the signing domain. If no DKIM-Signature field exists, this checker cannot infer the intended selector. Consult the sending service's DKIM configuration instead of assuming that the selector is "default."
No. This checker evaluates the public DNS record for one domain-selector pair. A DKIM result for an actual message also depends on its signature parameters, signed headers and body, canonicalization, and whether the signature verifies against the published key. Use the message's Authentication-Results header or a message-level DKIM verifier to investigate an individual delivery.
The behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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