For those of us running an email service, Reverse DNS Entry is an imperative service. If you run your own e-mail server, reverse DNS must exist for the IP address that outgoing e-mail is sent from. Not to worry if you host multiple domains on one e-mail server, you can setup reverse DNS to point to whichever domain name you consider primary. As well, if you are trying to locate where a site visitor came from or where an email message originated, this service will provide the information you’re looking for. For more information on this service, see:(Ali to provide link)