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DKIM record checker
Short answerThe DKIM checker looks up the public key a domain publishes for DKIM signing, at a selector you enter or at common selectors, and checks that the key is valid, not revoked and at least 1024 bits, ideally 2048.
Leave the selector empty to scan common ones (Google Workspace, Microsoft 365, Zoho, iCloud and popular sending services).
Lookups run in your browser through public DNS-over-HTTPS resolvers (Cloudflare, then Google). We don't store what you check. Privacy
How to use it
Reading the result
- 1
Find your selector
Open an email you sent, view the original headers, and find s= in the DKIM-Signature header. Or leave the selector empty to scan common ones.
- 2
Run the check
The checker fetches selector._domainkey.yourdomain and decodes the key.
- 3
Check the key length
2048-bit RSA keys are recommended. 1024-bit keys still work but are weaker; anything shorter is rejected.
- 4
Turn off testing mode
If the record has t=y, remove it once setup is complete.
- DKIM (DomainKeys Identified Mail)
- DKIM adds a cryptographic signature to each email. The receiver fetches the public key from DNS at selector._domainkey.yourdomain and verifies that the message wasn't changed and really comes from your domain. More about DKIM
FAQ
DKIM checker questions
What is a DKIM selector?
A selector is a name that lets a domain publish several DKIM keys, one per sending service. Microsoft 365 uses selector1 and selector2, Google Workspace uses google by default, and other services choose their own.
Why can't the checker find my DKIM key?
Your provider probably uses a custom selector. Find s= in the DKIM-Signature header of a sent email and enter it. If there is no DKIM-Signature header, DKIM isn't enabled for your domain yet.
Is 1024-bit DKIM still OK?
It is accepted, but 2048-bit keys are the current recommendation. Most providers let you rotate to a 2048-bit key in the admin console.
Go deeper: SPF, DKIM and DMARC explained. Fix it for good with deliverability monitoring.
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