How reverse DNS works
Reverse DNS maps an IP address to a name using a PTR record stored under a special domain (in-addr.arpa for IPv4, ip6.arpa for IPv6). Only whoever controls the address block — usually the ISP or hosting provider — can set it.
Forward confirmation checks that the returned hostname resolves back to the same IP. Mail servers rely on this: mail from an address without matching (forward-confirmed) reverse DNS is often rejected as spam.
Common uses
- Identifying servers and providers in logs and traceroutes.
- Checking email server configuration before sending mail.
- Complementing IP lookup when investigating an address.
Questions
Why does my IP have no reverse DNS?
Many ISPs don't set PTR records for home connections, or use generic ones. It doesn't affect browsing.
How do I set reverse DNS for my server?
Ask the provider that owns the IP address (your hosting company or ISP). Most hosting control panels have a reverse DNS or PTR setting.