DKIM checker and selector lookup
Paste up to 25 domains. We try the common DKIM selectors (or the one you enter), read each public key and check its size.
OK Worth fixing Broken Could not tell. Click a row for the records and the fix.
Selectors we try
default, dkim, google, selector1, selector2, k1, mail, s1, plus the selector you enter. Together they cover Google Workspace, Microsoft 365, Mailchimp, cPanel, ISPmanager, Plesk and most self-hosted Exim and Postfix setups.
What a DKIM record looks like
dkim._domainkey.example.com. 3600 IN TXT "v=DKIM1; k=rsa; p=MIIBIjANBgkqh..."
The long p= value is the public key. An empty p= means the key was revoked. Long 2048-bit keys are split into several quoted strings inside one TXT record; that is normal.
Questions
What is a DKIM selector?
The name under which a DKIM public key is published: selector._domainkey.yourdomain.com. Your mail host chooses it. Google Workspace uses "google", Microsoft 365 "selector1" and "selector2", cPanel and ISPmanager often "default" or "dkim".
How do I find my DKIM selector?
Open any email you sent, view the original message, and find the DKIM-Signature header. The s= value is the selector. Enter it in the selector field above.
What key size should DKIM use?
2048-bit RSA. 1024-bit keys still work but are the minimum; receivers ignore keys under 1024 bit.
Why do you not find my DKIM key?
Either the selector is not one of the common ones (enter yours), or DKIM is not turned on at your mail host. Turn it on in the host panel and publish the TXT record it gives you.
Can I check DKIM for many domains at once?
Yes, up to 25 domains per run. If they all use the same mail host, enter its selector once and it is tried for every domain.
More free tools: Mail health checker · DMARC checker · SPF checker · MX lookup
Run 10, 30 or 100 domains?
MXDeck is a Mac email app with this check built in: one inbox for every contact@, and a red dot the day a domain’s mail breaks.