What Does Reverse DNS (rDNS) Mean?
Reverse DNS (rDNS or RDNS) is a Domain Name Service (DNS) lookup of a domain name from an IP address. A regular DNS request would resolve an IP address given a domain name; hence the name “reverse.”
Techopedia Explains Reverse DNS (rDNS)
Reverse DNS requests are often used for filtering spam. Spammers can easily set the sending email address using any domain name they want, including legitimate domain names like those of banks or trusted organizations.
