Reverse DNS Lookup
Look up PTR records for an IP and validate forward-confirmed reverse DNS (FCrDNS). Use the DNS Lookup Tool for forward lookups or DNS Health Check for domain health.
Reverse DNS (PTR) + FCrDNS
Reverse DNS checks the PTR record for an IP address and validates forward-confirmed reverse DNS (FCrDNS): the hostname from PTR should resolve back to the same IP.
- PTR record lookup (IP → hostname)
- Forward A/AAAA lookup for each PTR hostname
- FCrDNS status: Valid, Mismatch, or Missing PTR
Tip: Enter an IPv4 or IPv6 address. Missing PTR often impacts email deliverability for mail servers.
What is reverse DNS (PTR)?
Reverse DNS maps an IP address back to a hostname via PTR records. Many mail servers and security checks use it to verify that the server is authorized to send for that hostname.
Why FCrDNS matters for email
Forward-Confirmed reverse DNS (FCrDNS) means the PTR for an IP points to a hostname that in turn resolves back to that IP. It improves deliverability and reduces the chance of being flagged as spam.
How to fix missing PTR
PTR records are set by the party that owns the IP (your host or ISP). Request a PTR record that points to your mail hostname (e.g. mail.yourdomain.com), then confirm with this tool and a forward DNS Lookup.
Next steps