Glossary
What is DKIM?
Verifies email messages using a cryptographic signature.
A mail service using DKIM signs selected message headers and the body; the receiver checks that signature with a public key published in DNS. Save the selector name and TXT key exactly as supplied by your provider. The query name typically combines the selector, _domainkey and the domain name.
Example
With selector selector1, query TXT for selector1._domainkey.example.com. Your mail provider supplies the real key value.
Common issue
A record under the wrong selector or with an incomplete key can break signature checks. Finding a DKIM key in DNS does not by itself show that a particular message has a valid signature.