A PTR record maps an IP address back to a hostname. It powers reverse DNS and is checked heavily by mail servers.
PTR records are the mirror image of A and AAAA records: instead of turning a name into an address, they turn an address back into a name. They live in special reverse zones (in-addr.arpa for IPv4 and ip6.arpa for IPv6) and are usually managed by whoever controls the IP block, which for most people means their hosting provider or ISP rather than their DNS panel. That split ownership surprises people who expect to set reverse DNS next to their other records.
Reverse DNS matters most for outbound email. Many receiving servers reject or heavily penalize mail from an IP whose PTR record is missing or does not match the sending host name, treating it as a sign of spam. If you run your own mail server, a correct and consistent PTR is essential for deliverability. This checker looks up the PTR for an address from several resolvers so you can confirm the reverse mapping is present and identical everywhere. Because reverse zones are delegated like any other, PTR changes propagate on their own TTL and can lag behind forward records.
Frequently asked questions
- Where do I set a PTR record?
- With the owner of the IP address, typically your hosting provider or ISP, not in your normal DNS zone.
- Why does my mail get flagged as spam?
- A missing or mismatched PTR record is a common reason receivers distrust a sending IP.