🔄 Reverse DNS
The Reverse DNS tool (rDNS) does the opposite of a normal lookup: it takes an IP address and finds the hostname assigned to it via a PTR record. Forward DNS maps name→IP; reverse DNS maps IP→name.
What it does
The Reverse DNS tool (rDNS) does the opposite of a normal lookup: it takes an IP address and finds the hostname assigned to it via a PTR record. Forward DNS maps name→IP; reverse DNS maps IP→name.
How to use it
Enter an IP address and run the lookup. The tool queries the special in-addr.arpa (IPv4) or ip6.arpa (IPv6) reverse zone to return the PTR hostname, if one is configured.
Real-world example
Mail servers commonly check a sender's reverse DNS. If your mail server's IP has no PTR record (or one that doesn't match its HELO name), recipient servers may reject or spam-folder your mail. A Reverse DNS lookup quickly tells you whether that record is set correctly.
Frequently Asked Questions
Does every IP have a reverse DNS record?
No. Many residential and mobile IPs have no PTR record at all. Having one is most important for mail servers and other public-facing services.
Is reverse DNS the same as forward DNS?
They are separate zones. A name may point to an IP without that IP pointing back to the same name. They must be configured independently, usually by the IP's owner or ISP.
Why do email servers care about rDNS?
A valid, matching PTR record is a basic anti-spam signal. Many receivers treat missing or mismatched rDNS as a sign of a poorly managed or abusive mail server.