GLOSSARY

What is reverse DNS (PTR)?

Reverse DNS maps an IP address back to a hostname via PTR records — important for email deliverability. Learn how it works.

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Reverse DNS is the opposite of a normal lookup: instead of name-to-IP, it maps an IP address back to a hostname using a PTR record. It is most visible in email, where receiving servers check it to judge legitimacy.

How PTR records work

A PTR record lives under the special in-addr.arpa (IPv4) or ip6.arpa (IPv6) zone and answers "what hostname owns this IP?". Unlike forward DNS, PTR records are controlled by whoever owns the IP block — usually your hosting provider or ISP, not you.

Why email cares

Mail servers often reject or spam-score messages from IPs with no PTR record, or whose PTR does not match the sending domain (forward-confirmed reverse DNS). If you run a mail server, a correct PTR is essential for deliverability.

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FAQ

Who controls reverse DNS?›
The owner of the IP block — typically your hosting provider or ISP, not the domain owner.
Why does email need reverse DNS?›
Receiving servers use PTR records to judge legitimacy; a missing or mismatched PTR hurts deliverability.

Related

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