Reverse DNS lookup
Find the hostname an IP address points back to.
A reverse DNS (PTR) record maps an IP address back to a hostname. Enter an IP to see its PTR record — important for mail deliverability (many servers reject mail from IPs without matching reverse DNS) and for making sense of server logs.
Frequently asked questions
Why does my mail server need reverse DNS?
Receiving servers often check that a sending IP has a PTR record that matches its forward DNS. Missing or mismatched reverse DNS gets mail flagged or rejected.
Who sets the PTR record?
The owner of the IP block — usually your hosting provider or ISP — sets reverse DNS, not your domain registrar.
What is "forward-confirmed reverse DNS" (FCrDNS)?
It means the PTR record for an IP resolves to a hostname that, in turn, resolves back to that same IP. Many mail and security systems require this round-trip match before trusting a sender.
Why does my IP have no PTR record?
Reverse DNS isn't set up by default on many hosts and home connections. You usually request it from your hosting provider or ISP, who controls the reverse zone for the IP block.
Can one IP have multiple PTR records?
Technically yes, but it's discouraged — many validators expect a single PTR per IP, and multiple records can cause inconsistent or failed checks. Stick to one hostname per address.
How is a PTR lookup different from a normal DNS lookup?
A forward lookup takes a name and returns an IP; a reverse (PTR) lookup takes an IP and returns a name, using the special in-addr.arpa (IPv4) or ip6.arpa (IPv6) zones.
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