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Reverse DNS Mismatch — a condition where a sending IP's PTR hostname does not resolve forward to that IP or conflicts with the hostname the mail server presents.
The mechanism complements SPF, DKIM, DMARC, or TLS and addresses a separate need, such as preserving authentication through forwarding, validating a brand, defining an encryption policy, or reporting failures. It does not replace baseline email authentication.
Reverse DNS Mismatch — a condition where a sending IP's PTR hostname does not resolve forward to that IP or conflicts with the hostname the mail server presents.
It conveys an additional verifiable signal between sender and receiver when ordinary authentication or transport encryption is insufficient for a specific delivery scenario.
Establish correct DNS, SPF, DKIM, DMARC, and TLS first, then satisfy the selected specification. Verify reports and actual message headers, not only the presence of a DNS record.
