Separation of concerns
I've made two separate articles out of Reverse DNS and Forward-confirmed reverse DNS (FCrDNS). Reverse DNS is fairly simple, and useful for getting information about an IP address. Not much controversy here. FCrDNS is a problematic method used in Email authentication. The more specialized article can go into more detail and discuss the concerns about security that are specific to email.
The topics overlap, but I don't consider either one to be a subtopic of the other. --David MacQuigg 22:38, 28 October 2009 (UTC)