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Reverse DNS (PTR) Lookup

Reverse DNS (a PTR record) maps an IP address back to a hostname. Mail servers are widely rejected without one, and the best practice is forward-confirmed reverse DNS (FCrDNS): the PTR host must resolve back to the same IP. Enter an IP directly, or a domain to check its mail server's IP.

Reverse DNS Lookup, FAQ

What is reverse DNS / a PTR record?
A PTR record maps an IP address to a hostname, the reverse of an A record. Mail servers use it to sanity-check the sending IP.
What is FCrDNS?
Forward-confirmed reverse DNS means the PTR hostname of an IP resolves (via its A record) back to that same IP. Receivers treat mail from IPs without valid FCrDNS as far more suspicious.
Why does reverse DNS matter for email?
Sending mail from an IP with no PTR, or a PTR that doesn't forward-confirm, is one of the fastest ways to land in spam or be rejected outright.

Want the complete picture? The Deliverability Radar scores a domain or IP out of 100 across DNS, authentication, reputation and connectivity, and emails you a branded PDF.

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