Question 1

What is a reverse DNS lookup?

Accepted Answer

A reverse DNS lookup finds the hostname (domain name) associated with an IP address by querying its PTR record. It's the opposite of a regular DNS lookup which finds the IP for a domain.

Question 2

Why would an IP have no PTR record?

Accepted Answer

Not all IPs have PTR records configured. The IP owner must set up a PTR record with their hosting provider or ISP. Residential IPs often have generic PTR records, while many cloud IPs have none.

Question 3

What is a PTR record used for?

Accepted Answer

PTR records are primarily used for email authentication. Mail servers check if the sending IP has a valid PTR record that matches the domain. Missing or mismatched PTR records can cause emails to be flagged as spam.

Reverse DNS Lookup