Level: Intermediate
DKIM (DomainKeys Identified Mail) adds a cryptographic signature to outgoing messages, letting receiving servers verify the message wasn't altered in transit and genuinely originated from the claimed domain.
A Public Key Is Published in DNS
The domain publishes a public key as a DNS TXT record at a specific selector subdomain, which receiving servers use to verify the signature attached to incoming mail.
The Private Key Signs Outgoing Messages
Your sending infrastructure uses a corresponding private key to generate a unique signature for each outgoing message, added as a DKIM-Signature header.
Selectors Allow Multiple Keys per Domain
The selector value in the DKIM record lets a domain maintain multiple signing keys simultaneously, useful for key rotation or supporting several sending sources independently.
Next step: Use the Find DNS Records to check your domain's published DKIM record to confirm the public key is correctly configured at the right selector.