Free tools / DKIM Checker
DKIM record checker
DKIM signs outgoing mail with a private key and publishes the matching public key in DNS under a selector. Receivers fetch the key at selector._domainkey.yourdomain.com and verify the signature. If the record is missing, malformed or revoked, every signed message fails authentication.
You need the selector to check a record, and the selector is in the DKIM-Signature header of any message the domain sends (the s= tag). Google Workspace uses google, Microsoft 365 uses selector1 and selector2, Mailchimp uses k1, and most others use s1 or default.
What you get back
Key published. Whether a valid DKIM record with a p= public key exists at the selector.
Key length. 1024 or 2048 bits. Several receivers now treat 1024-bit keys as weak.
Flags. Test mode (t=y), hash algorithms and key type.
Issues. Missing record, empty key (revoked) and weak key, with what to do.
How to use it
- Enter the domain and the selector from the DKIM-Signature header.
- Press Check DKIM.
- If the key is missing, republish it from your mail provider's admin panel. If it is 1024-bit, rotate to 2048.
Who uses this
Anyone setting up a mail provider. The DKIM step is the one most often skipped or mistyped. Confirming the key is live takes ten seconds.
Deliverability teams. DKIM alignment is what most senders rely on for DMARC, so a broken selector breaks DMARC too.
Cold email operators rotating domains. Each new sending domain needs its own key confirmed before warmup starts.
Same check, in your code
One API key, one credit pool, 1,000 free lookups to start. Phone, email, IP and DNS checks from a single endpoint, and you only pay for lookups that return an answer.
Start free Read the docsQuestions
Where do I find my selector?
Send yourself an email from the domain, view the raw headers, and look for s= inside the DKIM-Signature header.
The record exists but shows an empty key. What happened?
An empty p= tag means the key was deliberately revoked. Generate a new key pair in your mail provider and publish the new record.
Is 1024-bit still acceptable?
It works but it is on the way out. Rotate to 2048-bit when convenient; most providers offer it in one click.
Can I have multiple DKIM records?
Yes, one per selector. Each sending service usually gets its own selector, which is fine.