Reverse DNS Lookup
Look up the hostname (PTR record) associated with any IPv4 or IPv6 address. Useful for verifying mail server configuration and identifying hosts.
What Is Reverse DNS?
Reverse DNS (rDNS) maps an IP address back to a hostname using PTR records. While forward DNS resolves example.com to an IP, reverse DNS does the opposite - converting an IP address like 93.184.216.34 back into a domain name. This is sometimes called an IP-to-hostname lookup.
Why Is Reverse DNS Important?
- Email deliverability: Mail servers check PTR records to verify sending servers. Missing PTR records often cause emails to be flagged as spam.
- Security auditing: Identify which hostnames are associated with suspicious IP addresses in your logs.
- Network diagnostics: Verify that PTR records match forward DNS records (forward-confirmed reverse DNS or FCrDNS).
How to Set Up a PTR Record
PTR records are managed by whoever controls the IP address block, usually your hosting provider or ISP. Contact them to create or update a PTR record that maps your server IP back to your domain name. For email servers, the PTR should match the EHLO/HELO hostname.
Related Tools & Guides
- Forward DNS Lookup - resolve a domain name to its A, AAAA, MX, TXT, and NS records.
- DNS Leak Test - check whether your DNS queries are leaking outside your VPN.
- IP Lookup - view geolocation, ASN, and ownership data for any IP address.
- How to Prevent DNS Leaks - configure your VPN to keep DNS queries private.
Frequently Asked Questions
Why does my IP have no PTR record?
Most residential IPs and some cloud providers do not configure PTR records by default. If you need one for email sending, ask your hosting provider to create a PTR record pointing your server IP to your domain.
Does reverse DNS affect email delivery?
Yes. Many mail servers reject or flag messages from IPs without valid PTR records. For best deliverability, your PTR record should match the hostname your mail server uses in its EHLO greeting, and that hostname should have a matching A record.
What is forward-confirmed reverse DNS (FCrDNS)?
FCrDNS is a verification method where the PTR hostname is checked against forward DNS to confirm it resolves back to the original IP. This double check is used by anti-spam systems to verify server identity.