Reverse DNS maps an IP address to one or more hostnames using PTR records — the opposite direction of normal DNS A/AAAA lookups.

What is a PTR record?

A PTR (pointer) record lives in a special reverse zone (in-addr.arpa for IPv4) and stores the canonical hostname for an IP.

Can every IP have a PTR record?

Only if the IP owner configures reverse DNS. Many residential IPs have generic or no PTR records.

Receiving servers check that the sending IP’s PTR matches the server’s HELO/EHLO name and forward DNS — mismatches increase spam scores.

Request a PTR change from your hosting provider, ISP, or IP allocator. You cannot set PTR in public DNS alone without controlling the IP block.

DNS Tools

Find hostnames associated with an IP address using PTR records and reverse DNS queries.