Generic SMTP DKIM alignment error
SMTP 5.7.22: no valid author-matched DKIM signature
5.7.22 means no valid DKIM signature matched the author domain. A key can exist and a signature can even pass for another domain while still failing the alignment expected for the visible From address.
A receiver may report:
550 5.7.22 No valid author-matched DKIM signature found
The 5.x.x result is permanent for this message. Correct the signing identity or message path, then send a new test.
What author-matched means
Compare the visible RFC5322 From domain with the valid DKIM signature's d= domain under the receiver's alignment rules. A provider's shared signing domain may validate cryptographically but not represent your author domain.
How to diagnose and fix it
- Preserve the original From and every DKIM-Signature header.
- Verify which signatures pass cryptographically.
- Compare each passing
d=with the visible From domain. - Enable custom-domain DKIM in the sending service or correct its domain assignment.
- Publish only the selector values generated by that service and send a fresh test.
Do not change the visible From domain solely to make an unrelated provider signature align unless that identity change is intentional and user-visible.
Frequently asked questions
What does SMTP 5.7.22 mean?
No valid DKIM signature matched the author domain required by the receiver.
Can DKIM pass but fail alignment?
Yes. A signature can validate for a domain that does not align with the visible From domain.
Does MailFixIt calculate message-level alignment?
No. It can inspect reported header results and current public keys, but it does not independently verify the original message signature and alignment.
Related email diagnostics
Primary sources: IANA SMTP Enhanced Status Codes registry, RFC 6376 DKIM, and RFC 9989 DMARC.