What is DKIM (DomainKeys Identified Mail)?
A cryptographic signature added to each message and checked against a public key published in DNS.
How it works in practice
The sending server signs chosen headers and the body with a private key; the receiver fetches the matching public key from a TXT record at selector._domainkey.domain and verifies the signature. A valid signature proves the message wasn't altered and that the signing domain authorised it. Unlike SPF it survives forwarding, because it travels with the message.
The common mistake
Signing with the email platform's own domain instead of your domain, so DKIM passes but doesn't align with your From address.
Check it yourself
Related terms
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