Reverse DNS (rDNS) Check — PTR Record Lookup
Enter an IP address to see its PTR record — the hostname the IP claims to be — and whether that name resolves back to the same address.
Who this is for: Mail administrators and deliverability engineers checking that a sending IP has matching forward and reverse DNS.
What reverse DNS is
Forward DNS turns a name into an IP: example.com → 203.0.113.10. Reverse DNS does the opposite: it asks DNS which name is associated with an address, and the answer is stored in a PTR record under the in-addr.arpa zone (ip6.arpa for IPv6).
A PTR record does not come from your domain's DNS panel. It is delegated by whoever owns the IP range — your hosting provider or ISP. This is why 'I set up my DNS correctly' and 'my reverse DNS is wrong' are frequently both true at once.
Why anyone outside email cares
Mail servers are the loudest users of rDNS, but not the only ones. Server operators use it to turn log lines full of addresses into readable hostnames, and some services use it as a cheap signal of legitimacy: a host that controls its own IP range usually sets a matching PTR record.
Reverse DNS and email deliverability
Most receiving mail servers reject or heavily distrust a connection from an IP with no PTR record, and many also check that the PTR hostname resolves forward to the same IP (a 'matching' or 'confirmed' rDNS). The standard behaviour is to greet the connection and, if the check fails, either reject it outright or score it as suspicious before any content is examined.
The practical result: if you run your own mail server from a VPS and skipped rDNS, you will see refusals that look like content problems but are not. Typical wording includes 'no PTR record found' or 'does not resolve to a valid hostname' in the rejection string your server logs.
How to set it up on your own server
1. Pick the hostname the IP should claim — usually something like mail.yourdomain.com, and it should be a name you actually control.
2. Set the PTR record. On almost all providers this is in the control panel where the IP is managed, not in your DNS zone. If your provider has no such setting, rDNS cannot be fixed on your side.
3. Create the matching A record for that hostname pointing back to the same IP. Both directions must agree or the rDNS is still considered unconfirmed.
4. Verify with a lookup, then re-test mail delivery. Propagation is usually fast for rDNS because you control both ends, but resolvers cache — allow for TTL.
Diagnosing a broken record
- No PTR record at all: the range owner never delegated the zone, or never set one. Contact your provider; many set rDNS on request.
- PTR points to a generic hostname: common on budget hosts. It technically exists but matches nothing, and receivers still distrust it.
- PTR and A record disagree: the record exists but is 'unconfirmed'. Usually a stale A record or a typo.
- PTR points to a former customer's domain: happens on recycled IPs. Ask for a new PTR, or a new IP if the provider's tooling cannot change it.
Frequently asked questions
Is reverse DNS the same as forward DNS?
No. Forward DNS maps a hostname to an IP. Reverse DNS maps an IP to a hostname using PTR records in the in-addr.arpa zone. Both are needed for a 'confirmed' rDNS.
Why does my VPS have no PTR record?
Because PTR records are delegated by the owner of the IP range, not by your domain's DNS provider. If your host does not let you set one, you cannot add it yourself.
Does missing reverse DNS really cause email to be rejected?
Yes. Many receiving servers refuse connections from IPs without a PTR record, or require that the PTR name resolves back to the same IP. It is one of the most common reasons a correctly configured mail server is still refused.
How quickly do PTR changes take effect?
Usually within minutes to a couple of hours, since both the zone and the record are controlled by the same party. Temporary failures are cached resolver results and expire with the previous TTL.
Related tools
PureIP — free IP lookup and network diagnostics: IP location, WHOIS, reverse DNS, reputation, blacklists, AI service reachability and global ping.