Reverse DNS (PTR)
Find the hostname behind an IP
Look up the PTR record for a public IP address — the reverse of a normal lookup, mapping an IP back to a hostname. Important for mail server reputation.
How to read the results
- 1.Enter a public IPv4 address.
- 2.We query its PTR record — the hostname the IP’s owner has published for it.
- 3.Mail servers are expected to have a matching reverse DNS entry; a missing or mismatched PTR hurts deliverability.
Why it matters
Receiving mail servers check reverse DNS as a spam signal. A sending IP with no PTR, or one that doesn’t match its hostname, is treated with suspicion.
Frequently asked questions
No PTR record — does it matter?
For a mail server, yes: many receivers penalise or reject mail from IPs without a valid reverse DNS entry.