Reverse IP Lookup

Reverse DNS (rDNS) is the opposite of a normal DNS lookup. While normal DNS translates domain names to IP addresses, reverse DNS translates IP addresses back to domain names.

This is done via PTR records (Pointer Records) in DNS. Reverse DNS is used by email servers to verify senders, and by network administrators for troubleshooting.

Common use cases

• Email delivery — many mail servers check that the sender's IP has a valid PTR record
• Troubleshooting — identify which server an IP belongs to
• Security — verify that an IP address actually belongs to the organization it claims to
• Logging — replace IP addresses with readable hostnames in log files

1. Enter the IP address you want to look up (IPv4 or IPv6)
2. Click "Look up" to fetch the PTR record (reverse DNS)
3. Check the result — hostname is shown if PTR is configured
4. If no hostname is returned, the owner of the IP block has not set up reverse DNS

Tip: To verify that the hostname matches the IP address, perform a normal DNS lookup on the hostname and check that it points back to the same IP. This is called forward-confirmed reverse DNS and is important for email servers.

Reverse DNS plays a central role in modern network and email infrastructure. Here are the main reasons to use and configure rDNS:

• Email delivery — Many mail servers (Gmail, Outlook, etc.) reject or mark email as spam if the sender's IP lacks a valid PTR record or if the hostname doesn't match. Correct rDNS significantly improves deliverability.
• Network security — When reviewing logs or security incidents, hostnames make it easier to identify sources. Missing or suspicious rDNS can indicate compromised servers or botnets.
• Troubleshooting — Instead of memorizing IP addresses, hostnames provide a readable identifier. Network administrators use this daily to trace issues.
• Compliance — Some industries and vendors require that outgoing email comes from servers with correctly configured reverse DNS as part of security requirements.

Reverse DNS is not configured at your domain registrar, but with whoever owns the IP addresses — usually your hosting provider or ISP.

1. Contact the IP owner — Hosting provider, VPS service or ISP. Only they can create PTR records for their IP blocks.
2. Choose a hostname — Typically mail.yourdomain.com for email servers, or server1.yourdomain.com. The hostname should point back to the IP (forward-confirmed).
3. Request PTR update — The provider sets the PTR record to your chosen hostname. This often takes minutes to a few hours.
4. Set A record — Create an A record for the hostname in regular DNS so that forward-confirmed reverse DNS matches.

Important: You cannot create reverse DNS yourself for IP addresses you lease — it requires access to delegated reverse DNS zones at the RIR/ISP.