Reverse DNS Lookup — Convert IP Address to Hostname
Convert any IP address to its hostname with a free reverse DNS lookup. Check PTR records instantly. Useful for email server verification and spam prevention.
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What Is Reverse DNS?
Reverse DNS (rDNS) is a lookup that goes from an IP address back to a hostname. Normal DNS answers "what's the IP of example.com?". Reverse DNS answers "what hostname does 93.184.216.34 claim?". Both use the same DNS protocol but query different zones.
What Are PTR Records?
PTR (pointer) records are the DNS records that power reverse DNS. They live in special reverse zones — in-addr.arpa for IPv4 and ip6.arpa for IPv6. Only the organization that owns an IP block (typically the ISP or hosting provider) can publish PTR records for those addresses.
How Reverse DNS Affects Email Deliverability
Receiving mail servers routinely check the sending IP's PTR record. If no PTR exists, or if it doesn't match the HELO/EHLO hostname, the message is heavily penalized — often rejected outright by Google, Microsoft, and Yahoo. Setting a clean PTR is the single highest-leverage fix for a self-hosted mail server.
How to Use the Reverse DNS Tool
Enter any IPv4 (e.g. 8.8.8.8) or IPv6 address into the input above and run the lookup. The tool queries the appropriate reverse zone and returns the PTR record if one is published. No PTR? You'll see an empty result — meaning the IP owner hasn't set one up.
Frequently Asked Questions
What is reverse DNS?+
Reverse DNS is the process of resolving an IP address back to its hostname. While forward DNS maps a domain to an IP address, reverse DNS maps an IP to a domain name using PTR records.
Why does reverse DNS matter for email?+
Many email servers check if the sending IP address has a valid reverse DNS record. If no PTR record exists, your emails may be marked as spam or rejected entirely.
Why does my reverse DNS lookup return nothing?+
Not every IP has a PTR record. PTRs must be configured by whoever owns the IP block — typically your ISP or hosting provider. If you need one, request it through your provider's control panel or support team.
Can I set my own reverse DNS?+
Only the owner of the IP block can. On most VPS hosts (DigitalOcean, Linode, Hetzner, AWS) you can set the PTR yourself from the control panel. On home connections, only the ISP can.
What is FCrDNS?+
Forward-Confirmed Reverse DNS means the PTR for an IP resolves to a hostname, AND that hostname's forward A/AAAA record resolves back to the same IP. It's a basic legitimacy test used by mail servers and security tools.
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