DKIM checker
Look up a DKIM key by selector and confirm it's published correctly.
This DKIM checker looks up the DKIM record at selector._domainkey.yourdomain.com and validates that a usable public key is published for the selector you provide. Because DKIM signatures are tied to a specific selector, you need to supply the one your mail provider uses, and the tool then confirms the key version, type, and that the value is well formed. A missing or truncated key means receivers cannot verify your signatures, which weakens authentication and DMARC alignment. After you confirm the selector resolves, SJ Monitor can keep an eye on it so a key rotation never quietly breaks signing.
Frequently asked questions
What is a DKIM selector?
A selector is a label that points to one specific DKIM key, letting a domain publish several keys at once. You can usually find it in the s= tag of a DKIM-Signature header on a sent message.
Why is my DKIM record not found?
Either the selector is wrong, the key was never published, or a DNS edit removed it. SJ Monitor's DNS monitoring continuously re-checks the selector and alerts you if the record disappears or changes.
Does DKIM need to be re-checked after key rotation?
Yes. Rotating keys publishes a new selector and key, and the old one may stop working, so verifying after each rotation prevents signing gaps.
What key length should a DKIM key be?
2048-bit RSA is the current recommendation; 1024-bit still works but is weaker and being phased out. The tool shows the key so you can confirm its strength.
Why is my published DKIM key marked invalid?
Usually the record was truncated or split incorrectly across multiple TXT strings, the p= value got mangled on paste, or a leading v=DKIM1 tag is missing. Re-publishing the exact value from your provider fixes it.
Can a domain publish more than one DKIM key?
Yes — that's the whole point of selectors. You can run several active keys under different selectors at once, which is how zero-downtime key rotation works.
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