DKIMSPFDMARC

DKIMSPFDMARC is a shorthand reference to a group of email authentication mechanisms collectively used to verify the origin of email messages and protect against spoofing. It encompasses DKIM (DomainKeys Identified Mail), SPF (Sender Policy Framework), and DMARC (Domain-based Message Authentication, Reporting, and Conformance). Deployed together, these standards increase the likelihood that legitimate messages are delivered and illegitimate ones are rejected or flagged. They rely on DNS records, cryptographic signatures, and policy definitions, and are widely supported by mail receivers and providers.

DKIM signs messages with a cryptographic header added by the sending domain. The signature is verified by the recipient using a public key published in DNS. DKIM helps ensure message integrity and verifies that the domain attributed in the signing header is the same as the sending domain, even if the message is relayed.

SPF allows a domain owner to publish which hosts are authorized to send mail on behalf of that domain. The recipient checks whether the sending IP address is listed in the domain's SPF record for the envelope sender (the MAIL FROM) domain. SPF does not authenticate the From header directly, but it contributes to overall evaluation when combined with DMARC.

DMARC builds on DKIM and SPF by requiring alignment between the authentication results and the From header domain. A domain publishes a DMARC policy in DNS specifying how to handle messages that fail DKIM or SPF authentication (none, quarantine, or reject) and provides reporting to the domain owner.

Deployment considerations include proper DNS records, key management and rotation for DKIM, policy selection, and monitoring through aggregate and forensic reports. Limitations include handling of forwarded or redistributed mail, subdomain responsibilities, and potential deliverability impacts if misconfigured. DKIM, SPF, and DMARC are formalized in RFCs: DKIM (RFC 6376), SPF (RFC 7208), and DMARC (RFC 7489).