DKIM Checker

Look up DKIM public key records. Enter a domain and selector — find the selector in your email headers or use a common one from the list below.

// Microsoft 365 / Office 365

Microsoft 365 uses two rotating selectors: selector1 and selector2. Try both — only one is active at a time. The active selector signs outgoing mail. If you can't find your selector, check the DKIM-Signature header in a sent email for s=selectorX.

// common selectors — click to autofill

Quick selectors:

// how dkim works

DKIM (DomainKeys Identified Mail) works by having your mail server sign outgoing emails with a private key. The corresponding public key is published in DNS at selector._domainkey.yourdomain.com.

Receiving servers look up this public key and use it to verify the signature in the email's DKIM-Signature header. If valid, the email passes DKIM authentication.

To find your selector: look at the raw headers of an email you sent. Find the DKIM-Signature header and look for s=yourSelector.