Reverse DNS Lookup

A PTR (pointer) record maps an IP address back to a hostname — the reverse of an A or AAAA record. It lives in a special zone: in-addr.arpa for IPv4 and ip6.arpa for IPv6.

PTR records are set by whoever controls the IP block — usually your hosting provider or ISP, not your domain registrar. If no PTR exists, contact the provider that assigned you the IP and ask them to set one.

FCrDNS means the PTR hostname resolves back to the original IP address. Mail servers check for it: an IP whose reverse DNS does not forward-confirm is far more likely to have its email rejected or marked as spam.

Set the PTR record with your hosting provider so the hostname matches a name whose A or AAAA record points back to the same IP. For mail servers, use a dedicated hostname like mail.example.com rather than a generic ISP name.