What is Reverse DNS?
Reverse DNS is name resolution that looks up an IP addresss to obtain a domain name, performing the opposite function of the DNS server which is to turn names into IP addresses.
Reverse DNS can be used as a spam filter. Typically spammers use invalid IP addresses, ones that do not match domains. A reverse DNS program looks up the IP addresses of incoming messages and if no valid domain name is found, the server will block that message. Although reverse DNS is fairly effective for filtering spam, it also often blocks valid emails.
Our administrators configure reverse DNS on all of our servers. However, if you administrate your own server, you may contact your IP address’ provider to configure reverse DNS.
NOTE: Setting up a PTR record in attempt to configure reverse DNS will not work properly.
For more information on Reverse DNS, please see the following URL: http://member.dnsstuff.com/help/index.html