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Enter an IP address to find its hostname and check that forward and reverse DNS match.
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Reverse DNS maps an IP address back to a hostname through a PTR record. Mail servers use it as a basic check on every server that connects to them.
A PTR record lives under in-addr.arpa, for example 10.113.0.203.in-addr.arpa for 203.0.113.10. It names the host behind the IP.
Forward-confirmed reverse DNS (FCrDNS) means that hostname also has an A record pointing back to the same IP. That two-way match is what receivers look for.
Gmail requires valid forward and reverse DNS for sending IPs, and many other servers reject or filter mail from IPs without a PTR.
A hostname on your own domain, such as mail.acme.com, looks better than a generic name built from the IP, which is typical of home connections.
The PTR record is controlled by whoever owns the IP block: your cloud provider, hosting company or ISP. Most cloud panels have a reverse DNS setting on the IP itself.
Create the A record for the hostname first, then set the PTR to that hostname. If you send through Google Workspace, Microsoft 365 or an email service, they handle this for their IPs.
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A reverse DNS lookup finds the hostname for an IP address by reading its PTR record. It is the opposite of a normal lookup, which finds the IP for a hostname.
If you run your own mail server, yes. Gmail requires sending IPs to have valid forward and reverse DNS, and many receivers reject mail without it. With Google Workspace or Microsoft 365, the provider sets it for you.
Only the owner of the IP block, usually your hosting provider, cloud platform or ISP. Your domain registrar cannot set it, because the record lives in the in-addr.arpa zone of the IP owner.
It means the PTR hostname for an IP has an A record that points back to that same IP. Mail servers check this because anyone who controls an IP block can put any name in its PTR.
Not yet. It checks IPv4 addresses only. Enter the IPv4 address of your mail server.
