I also have a query re Reverse DNS. I registered with MxToolbox a few days ago during attempts to de-list spam blacklistings. One of the things that was highlighted was the need for Reverse DNS.
Yesterday I got our ISP to add the neccessary PTR Record and I now get a satisfactory Reverse DNS resolution from lookupserver.com - my problem is that MxToolbox is still flags it as a problem. Is there something else that needs doing or should I just be more patient?