Reverse DNS – what does it mean?
Reverse DNS, or simply rDNS, is a mechanism for translating an IP address into its matching domain name. Compared to the standard Forward DNS lookup, which resolves the domain name to its IP address, it serves the exact opposite purpose.
You can use it to establish that a specific IP address corresponds to a particular domain name. One of the most common reasons for using it is establishing trust in email servers. They use Reverse DNS lookups to make sure the email came from a legitimate source and isn’t a hoax.