Reverse DNS Lookup
Find the hostname associated with an IP address (PTR record).
About Reverse DNS Lookup
What is Reverse DNS?
Reverse DNS (rDNS) is the process of resolving an IP address back to a hostname. While forward DNS maps domain names to IP addresses (A records), reverse DNS maps IP addresses to domain names (PTR records). PTR records are stored in a special domain called in-addr.arpa for IPv4 and ip6.arpa for IPv6.
Why We Built This Tool
Reverse DNS lookups are critical for email deliverability, security auditing, and network troubleshooting. Mail servers check PTR records to verify that sending servers have valid reverse DNS, which helps prevent spam. This tool provides instant rDNS lookups without needing dig, nslookup, or host commands.
How to Use It
Enter an IP address (IPv4 or IPv6) and click Lookup. The tool queries the DNS system for PTR records associated with that IP and returns the hostname(s) it resolves to. If no PTR record exists, the result will indicate that no reverse DNS entry was found.
Email & Reverse DNS
Email servers (Gmail, Outlook, Yahoo) check that the sending server's IP has a valid PTR record that matches the server's HELO/EHLO hostname. Missing or mismatched reverse DNS is a major cause of email being flagged as spam. If you run your own mail server, ensure your ISP or hosting provider has set up correct PTR records.
Common Use Cases
Verifying mail server PTR records for email deliverability, identifying the owner of an IP address, investigating suspicious network connections, auditing server configurations, checking if CDN or cloud provider IPs have proper reverse DNS, and troubleshooting SMTP rejections due to missing PTR records.