DKIM checker: find and test your DKIM keys
Look up your DKIM public keys and check their length and format. Enter a selector, or let us try the names common email providers use.
Reads public DNS records only.
- Passed
- 0
- Warnings
- 0
- Problems
- 0
- Checked
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How it works
Find and test your DKIM keys
Check that the public keys behind your email signatures are published, readable and strong enough.
Enter your domain
Add your selector if you know it. Otherwise we try over 30 selector names used by common email providers.
We look up the key
The checker reads the key at selector._domainkey.yourdomain and checks its format and length.
See what to fix
Every key found is listed with its type and length, and any problem is explained.
Common selectors
Where providers store their keys
The selector is the s= value in the DKIM-Signature header of your email.
Google Workspace
Usually google.
Microsoft 365
selector1 and selector2.
Hostinger
hostingermail-a and similar names.
Mailchimp and Mandrill
k1, k2 and k3.
SendGrid
s1 and s2.
Others
Zoho, Mailjet, Brevo, Fastmail, Proton and more are tried automatically.
01
Use 2048-bit keys
Shorter keys are weaker, and keys under 1024 bits are rejected by many receivers.
02
One key per sending service
Each service that sends for you (mailbox, newsletter, CRM) should sign with its own key and selector.
03
Confirm with a real email
A published key does not prove your emails are signed. Send one to the mail tester to check the signature.
More email tools
Check the rest of your email setup
Domain scanner
SPF, DKIM, DMARC, BIMI, mail servers and blocklists in one scan.
SPF checker
Check your SPF record, its includes and the 10-lookup limit.
DMARC checker
See your DMARC policy, report addresses and next step.
BIMI checker
Check your logo record, SVG file and certificate.
Mail tester
Send one email and get a spam score out of 10.
What is DKIM?
DKIM (DomainKeys Identified Mail) adds a digital signature to every email you send. The receiving server checks it against the public key in your DNS, which proves the message came from your domain and was not changed.
What is a DKIM selector?
The name under which a key is stored, for example google or selector1. You find it as the s= value in the DKIM-Signature header of any email you sent.
How long should my DKIM key be?
2048 bits is the recommended length. 1024-bit keys still work but are weaker, and shorter keys are rejected by many receivers.
The checker found a key. Does that mean DKIM works?
It means the key is published correctly. To check that your emails are actually signed with it, send one to the mail tester.
Try it
Are your emails signed?
Check your DKIM keys now, then confirm with a real email.
More tools: Website checker · DNS checker · Domain scanner · SPF checker · DMARC checker · BIMI checker · Mail tester