Definition
DKIM adds a digital signature to outgoing emails using a private key, while a corresponding public key is published in your DNS as a TXT record. Receiving servers verify the signature against your public key. If the email content was modified in transit, the signature fails. DKIM is non-negotiable for bulk senders since 2024.
Example
Selector: _domainkey.yourdomain.com. Record: v=DKIM1; k=rsa; p=MIGfMA0...