DKIM signing: authenticate the domain and message integrity

DKIM adds a cryptographic signature that lets recipients verify the signing domain and detect changes to signed message content.

DomainKeys Identified Mail signs selected headers and the message body using a private key. Receiving systems retrieve the corresponding public key from DNS and verify that the signed content still matches.

Deploy DKIM through AuthSMTP

  1. Enable DKIM for the domain in the AuthSMTP Control Panel.
  2. Publish the selector record exactly as supplied.
  3. Wait for normal DNS propagation.
  4. Send through the real AuthSMTP route.
  5. Check that DKIM passes and that its signing domain aligns for DMARC.

A DNS record alone does not prove that an application used the correct account or that the outgoing message was signed. Equally, modifying signed content after AuthSMTP has processed it can invalidate the signature.

Use our DKIM setup FAQ for AuthSMTP-specific steps. You can check a selector at dkim.org and inspect an actual delivery with AuthEmailTest.com.

Key takeaway
Enable DKIM for every sending domain, publish the supplied DNS record and test a delivered message—not only the DNS entry.
Practical next step

Send from every active From domain and confirm a passing, aligned DKIM result in the received Authentication-Results header.

Using AuthSMTP

AuthSMTP can sign outgoing mail with the DKIM configuration created in the Control Panel. You publish the supplied DNS record and verify that the signing domain aligns with the visible From domain.