Free PTR Lookup
Enter an IPv4 or IPv6 address to read its PTR record, then see whether that hostname points back to the same address, the check receiving mail servers care about.
Reading the reverse record...
Could not check
No PTR record is published for this address.
What a PTR Lookup Tells You
A PTR lookup, also called a reverse DNS lookup, starts from an IP address and asks which hostname it claims. Ordinary DNS runs the other way, from a name to an address, so the reverse answer lives in a separate tree under in-addr.arpa for IPv4 and ip6.arpa for IPv6.
A PTR record on its own proves little, because whoever controls an IP can put any name in it. So this tool also looks up the hostname it finds and checks that the name resolves back to the same IP. That two-way match is called forward-confirmed reverse DNS, and it is what mail receivers look for. To find a domain's mail servers first, use the MX lookup.
- Enter a public IPv4 or IPv6 address, such as your mail server's sending IP.
- We turn the address into its reverse name and read the PTR record.
- We look up the hostname and compare its addresses with the IP you entered.
- Read the verdict. If it needs fixing, the change is made with whoever controls the IP.
What this check settles
- Whether the IP has a name: many receivers treat mail from an address with no PTR record as suspicious.
- Whether the name points back: a hostname that does not resolve to the same IP fails forward confirmation.
- Who an address belongs to: the hostname often names the host or network behind an IP in your logs.
Reverse DNS Results Explained
A lookup can end three ways. Here is what each means for a sending IP.
| Result | What we found | What it means | For mail |
|---|---|---|---|
| Forward confirmed | PTR and A/AAAA agree | The IP names a hostname and the hostname names the IP back. Reverse DNS is set up correctly. | Good |
| Not confirmed | PTR exists, no match back | The hostname has no address, or a different one. Add a matching A or AAAA record, or correct the PTR. | At risk |
| No PTR record | Nothing in the reverse zone | The address has no name at all. Ask whoever controls the IP to publish one. | At risk |
How to Read the Result
The verdict comes first, then the exact name queried and every hostname found.
The verdict
The headlineWhether reverse DNS exists and whether at least one hostname resolves back to the address you entered.
Name queried
The queryThe reverse name built from your IP. IPv4 octets are reversed under in-addr.arpa; IPv6 is expanded and reversed one hex digit at a time under ip6.arpa.
PTR hostnames
The answerEach hostname in the reverse record with its TTL. An address usually has one; if there are several, the first three are forward-checked.
Resolves back
The proofThe A and AAAA addresses of that hostname, and whether your IP is among them. That is the forward half of the check.
What a PTR Record Is
A PTR record maps an IP address to a hostname. For 192.0.2.25, the record sits at 25.2.0.192.in-addr.arpa and might point to mail.example.com.
The key difference from other records is who controls it. The reverse zone belongs to whoever was allocated the IP range, not to the owner of the domain in the answer, so you cannot set a PTR record at your registrar.
How to Set Up Reverse DNS
Most hosting and cloud providers offer a reverse DNS setting on each IP. On a business connection, you usually ask the ISP.
The usual sequence:
- Choose a hostname you control, such as mail.example.com.
- Publish an A or AAAA record for it pointing to the IP.
- Set the PTR with your host, or ask your ISP to.
- Use the same name in the mail server's HELO greeting, then run this check again.
Where Reverse DNS Goes Wrong
Most PTR faults come from the two halves being managed by different people. The common ones:
- A default hostname from the provider left in place, which resolves correctly but looks like a generic connection to spam filters.
- Trying to add the PTR record in your domain's DNS zone, where it has no effect. It belongs to whoever controls the IP.
- Moving a server to a new IP and updating the A record, while the new IP has no reverse record.
- Sending over IPv6 with reverse DNS set only on the IPv4 address. Each address needs its own record.
Why Reverse DNS Matters
Avoid refused mail
Major mailbox providers expect sending IPs to have valid forward and reverse DNS, and some receivers refuse mail without it.
Protect your reputation
A missing or generic hostname is a common spam signal, so it can weigh against mail that passes every other check.
Identify an address
A hostname turns an unknown IP in a log or mail header into a clue about the network behind it.
Verify a new server
Confirm a new sending IP has its reverse record in place before you route real mail through it.
Who Runs PTR Lookups
The same reverse lookup answers a different question depending on who runs it.
Mail & Server Admins
Confirm a sending IP passes forward-confirmed reverse DNS before it carries live mail.
For DNS monitoringSecurity Analysts
Put a name to an IP from a log, an alert or a message header during an investigation.
For IT & MSPsEmail Senders
Check a dedicated sending IP has its reverse record set before you start warming it up.
For marketersRelated Email & DNS Tools
Reverse DNS covers the IP. These cover the domain sending from it.
Find the mail servers
List a domain's MX hosts and their addresses, then run each one through this lookup.
MX lookupCheck deliverability
Read MX, SPF, DKIM and DMARC together to see the rest of the mail setup.
Email deliverability checkerCheck the forward record
See the A and AAAA records a hostname publishes, along with the rest of its zone.
Run a DNS lookupFrequently Asked Questions
Common questions about PTR records and reverse DNS.
What is a PTR lookup?
A DNS query that starts from an IP address and returns the hostname published for it. It is the reverse of an A or AAAA lookup, so it is also called a reverse DNS lookup.
How do I do a reverse DNS lookup?
Enter the IP address in the tool above. You can also run dig -x 192.0.2.25 from a terminal, which builds the reverse name for you.
What is forward-confirmed reverse DNS?
A two-way match. The IP's PTR record names a hostname, and that hostname's A or AAAA record contains the same IP. Because the two halves are often controlled by different parties, a match is stronger evidence than a PTR record alone.
Why does reverse DNS matter for email?
Receiving servers use it as a basic sign of a properly run mail server. Major providers ask senders to have valid forward and reverse DNS, and missing records can lead to mail being refused or sent to spam.
Who sets my PTR record?
Whoever controls the IP address, usually your hosting provider, cloud platform or ISP. Your registrar and your domain's DNS zone cannot set it, unless the reverse zone has been delegated to you.
What should my PTR record say?
A hostname you control that resolves back to the same IP, such as mail.example.com. For a mail server, it is best if the hostname also matches what the server announces in its HELO greeting.
Can an IP have more than one PTR record?
Yes, but it is rarely a good idea. Some software only reads the first answer, so a single record per address is the safest setup.
Why can I not look up a private IP?
Addresses such as 10.0.0.1 and 192.168.1.1 are not routed on the public internet, so there is no public reverse record to read. Their reverse names only exist on your own network.
Does IPv6 need reverse DNS too?
Yes, if you send mail over it. Each sending address needs its own PTR record under ip6.arpa, and some providers hold IPv6 senders to stricter rules.
Start Monitoring & Catching Domains Today
Join founders, agencies, and domainers already protecting their portfolio. Your first 5 domains are free.
No credit card required • Cancel anytime
Guides for domain operators
Deep dives on domain names, DNS, SSL, acquisitions and portfolio management.
All guides →
4 Letter Domains: The Complete LLLL Investing Playbook
4 letter domain names represent one of the most liquid segments of the domain aftermarket. All 456,976 possible .com combinations are registered.
.SI Domain: Slovenia's 30-Year-Old ccTLD Is Suddenly Super Intelligence
What is the .SI domain? Learn how Slovenia's country-code TLD went from 10 registrations in 1992 to a 2,199% surge in September 2026, and why 'super intelligence' made .SI the new .AI.
Infringing Domains: Detecting, Monitoring, and Recovering
Your domain is your storefront. Every day, someone registers a lookalike of it, to skim your traffic, phish your customers, or hold it for ransom. This guide covers what infringing domains are, how to find them before they hurt you, and exactly what to do when you do.