What this test tells you
Reverse DNS can help explain the label attached to a server or network address. It is useful for troubleshooting naming discrepancies, especially for mail infrastructure. A plausible hostname remains an operator-controlled label: even a confirmed round trip does not authenticate a person or service.
How to run the test
- Enter the public IPv4 or IPv6 address to inspect, keeping its address family clear.
- Run the lookup and inspect each resolver's PTR answers and response status.
- Read the forward confirmation for each returned name, alongside any missing records or lookup errors.
How the measurement works
The server constructs the reverse DNS name and asks the configured resolvers for pointer, or PTR, records. It then looks up A or AAAA records to check for the original IP.
System DNS and external DNS-over-HTTPS resolvers may be consulted. Forward checks use a bounded public lookup for the original address family; errors are distinguished from a completed mismatch.
Understanding your results
- Forward-confirmed name
- A PTR points to a name whose corresponding A or AAAA response includes the original IP. The naming relationship is consistent for this lookup.
- PTR without confirmation
- A returned name does not resolve back to the address in a completed check. This may reflect stale records, an intentional naming arrangement or configuration trouble.
- No PTR or indeterminate
- A successful lookup may find no reverse name. Resolver errors or incomplete forward checks instead leave the relationship unknown.
Compare before and after
- Save the IP, family, resolver results, names and record lifetimes before making a DNS change.
- Change one relevant PTR or forward record if you administer it, then repeat the same lookup.
- Allow for cached records before comparing resolver agreement. Keep a completed mismatch separate from a failed lookup.
Limits of the test
- Reverse DNS is often managed by the address provider rather than the domain owner.
- A resolver's DNSSEC authentication flag concerns validated DNS data, not the identity or trustworthiness of the named service.
What to change, if needed
- A mail server lacks the required reverse name
- Ask the IP provider about setting the PTR and align the intended forward record, then retest after caches expire.
- Resolvers disagree after an update
- Check the authoritative records and their time to live before changing them again.
Frequently asked questions
Is no PTR a privacy guarantee?
No. It only means no reverse name was returned; other network information remains available.
Can I change any IP's name?
No. Control of the reverse zone usually belongs to the organisation that manages the address block.