Why is a valid PTR record important for email deliverability?

PTR validity directly affects deliverability:

Receiver behavior:

Many receivers check PTR before accepting mail

No PTR = often rejected or deferred

Generic PTR = strong spam indicator

Reputation signals: Professional mail servers have professional rDNS. Spammers often use IPs without proper PTR.

Authentication complement: PTR does not replace SPF/DKIM/DMARC but adds another layer of legitimacy verification.

What qualifies as valid:

Exists (not NXDOMAIN)

Meaningful hostname (not IP-based or generic)

Forward-confirmed (A record matches)

Proper ship documentation is expected in every legitimate harbor. Missing papers invite inspection or rejection.