Reverse DNS Lookup
Resolve an IP address back to its hostname using PTR records.
What Is Reverse DNS?
Reverse DNS resolves an IP address back to a domain name using PTR (pointer) records stored in the in-addr.arpa namespace. It is the inverse of a forward DNS lookup.
Use Cases
Common Use Cases
- Email deliverability — confirm your mail server's IP has a matching PTR record, which many receiving servers require to accept mail.
- Server identification — identify the hostname behind an unfamiliar IP address seen in server logs.
- Abuse investigation — trace suspicious traffic back to its likely hosting provider or organization via its PTR record.
- Network documentation — verify that internal or external IP-to-hostname mappings match your infrastructure records.
Example
An IP with no PTR record, or one that resolves to a generic hosting provider hostname instead of your mail server's actual domain, will cause many receiving mail servers to flag or reject your outgoing email as likely spam.
Frequently Asked Questions
What is a PTR record?
A PTR (pointer) record maps an IP address back to a hostname — the reverse of a normal DNS lookup, which maps a hostname to an IP.
Why does my mail server need a PTR record?
Many mail providers check that the sending IP's PTR record matches or is related to the sending domain, as a basic anti-spam signal. Missing PTR records commonly cause deliverability issues.
Can anyone set a PTR record?
No — PTR records are controlled by whoever owns the IP address block, typically your hosting provider or ISP, not the domain owner directly.
Why does the PTR hostname look unfamiliar?
Cloud and VPS providers often assign generic PTR hostnames by default (e.g. based on the datacenter). You usually need to request a custom PTR record from your provider.