How to test local reverse dns lookups from your name server
I was having issues with reverse dns not working on one of the nameservers I admin and couldn’t figure out how to test it without changing the reverse dns delegation at my ISP, which I had implemented as a temporary fix to our issues (Hey take over our Reverse DNS, here are the records, quick, I can’t send any mail!!)
It took a while to find it, but this is how you can query your local DNS server for reverse response… write a nice nagios script around it and save yourself some embarrassment when the bosses ask why every email is bouncing saying invalid server. 
host -t ptr 4.3.2.1.in-addr.arpa ns.yournameserver.com