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AuthenticationA free tool by NullFortis
DKIM Checker
Check your DKIM signature
What is it?
DKIM (DomainKeys Identified Mail) adds a cryptographic signature to outgoing email and publishes the matching public key in DNS, so a receiver can verify the message wasn't altered in transit and really came from a server holding your private key.
Why it matters
SPF only checks the sending IP address; DKIM proves message integrity and sender authenticity independent of IP, which matters when mail is forwarded or relayed through another server.
Impact if ignored
A missing or broken DKIM signature makes mail more likely to be flagged as spam or rejected outright by strict receivers, and it undermines DMARC — which needs SPF or DKIM to both pass and align with your domain.
Common use cases
- Verify a sending platform's own DKIM selector is correctly published
- Confirm a recent key rotation didn't break signing
- Diagnose a "DKIM fail" result on a delivered message