Reverse DNS Lookup
Look up PTR records to find the hostname associated with an IP address. Essential for email deliverability.
About DNS Lookup
Complete DNS lookup tool that queries A, AAAA, MX, TXT, NS, CNAME, and other DNS record types from multiple global DNS servers.
Key Features
Multiple record types (A, AAAA, MX, TXT, NS, CNAME, SOA, CAA)
Multi-region DNS resolution
Propagation checking
TTL information
Reverse DNS lookup
PTR records provide reverse DNS (rDNS) lookup—the ability to find a hostname from an IP address. This is the opposite of forward DNS, which maps domain names to IP addresses. Reverse DNS is critical for email deliverability, security verification, and network troubleshooting.
Our reverse DNS lookup tool checks PTR records from multiple locations, helping you verify that your server's IP address properly resolves to your expected hostname. This is essential for email servers, as receiving mail servers routinely check that the sender's IP has a valid PTR record matching the sending domain—a practice called Forward-Confirmed reverse DNS (FCrDNS).
For complete email deliverability verification, also check your MX records for mail routing and TXT records for SPF, DKIM, and DMARC authentication. All three—PTR, MX, and TXT—must be properly configured for reliable email delivery.
**Methodology:** PTR record queries for IP addresses from 6 regions showing reverse DNS hostnames and FCrDNS validation.
Common DNS Errors & How to Fix Them
4 relevant issuesNo reverse DNS record exists for this IP address. This commonly causes email delivery issues as many mail servers reject connections from IPs without PTR records.
1) Verify missing PTR: dig -x YOUR_IP_ADDRESS (e.g., dig -x 192.0.2.1). 2) Cloud providers: AWS EC2 → Elastic IP → Actions → Update reverse DNS. DigitalOcean → Networking → PTR records. 3) VPS: Usually in control panel under "Reverse DNS" or "rDNS". 4) ISP/Dedicated: Contact support with desired hostname. 5) PTR should match your mail server HELO.
The PTR record points to a hostname, but that hostname doesn't resolve back to the same IP address. This breaks Forward-Confirmed reverse DNS (FCrDNS), causing email delivery and security verification failures.
1) Check PTR: dig -x YOUR_IP (note the hostname returned). 2) Check forward: dig HOSTNAME_FROM_PTR A +short. 3) They must match! If PTR returns mail.example.com, then dig mail.example.com A must return YOUR_IP. 4) Fix either: update PTR to a hostname you control, or add A record for the PTR hostname pointing to the IP.
The PTR record returns a generic hostname assigned by the ISP or hosting provider (e.g., "192-0-2-1.isp.com") rather than your actual domain. This looks unprofessional and may trigger spam filters for email.
1) Check current PTR: dig -x YOUR_IP +short. 2) Request custom PTR from provider (see ptr-not-found fix steps). 3) Set to: mail.yourdomain.com (must match SMTP HELO). 4) Ensure mail.yourdomain.com A record points back to the IP. 5) Verify: dig -x YOUR_IP should return your custom hostname.
The DNS server did not respond within the expected time. This can indicate network issues, overloaded nameservers, or firewall blocking.
1) Test NS connectivity: dig @ns1.example.com example.com +time=10. 2) Check if NS responds: nslookup example.com ns1.yourprovider.com. 3) Verify UDP port 53: nc -vzu ns1.example.com 53. 4) Test from different resolver: dig @1.1.1.1 example.com. If public resolvers work, your NS may be overloaded or blocking.
Frequently Asked Questions
4 relevant questionsPTR (Pointer) records provide reverse DNS lookup—they map an IP address back to a domain name, the opposite of A/AAAA records. When you look up "192.0.2.1", a PTR record returns the hostname associated with that IP. PTR records are stored in special zones (in-addr.arpa for IPv4, ip6.arpa for IPv6) and are typically managed by your hosting provider or ISP, not your regular DNS provider.
Email servers check PTR records to verify sender legitimacy. When your mail server connects, the receiving server does a reverse lookup on your IP to see if it matches your sending domain. Missing or mismatched PTR records cause emails to be rejected or marked as spam. A proper setup has forward-confirmed reverse DNS (FCrDNS): the PTR for your IP returns a hostname, and that hostname's A record points back to the same IP.
PTR records must be configured by whoever controls the IP address—usually your hosting provider, VPS provider, or ISP. In most hosting control panels (AWS, DigitalOcean, Linode), you can set "Reverse DNS" in the networking settings. For ISP-provided IPs, contact them directly. The PTR hostname should match your server's actual hostname, and that hostname should have an A record pointing back to the IP for proper FCrDNS.
PTR mismatch occurs when the reverse DNS hostname doesn't match the expected domain, or when forward DNS doesn't point back to the same IP. Common causes: 1) PTR not configured at all (returns generic ISP hostname), 2) PTR points to old hostname after migration, 3) Shared hosting IP with PTR set to another customer's domain, 4) IP address changed but PTR wasn't updated. Fix by contacting your hosting provider to update the PTR record.
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