I'm just curious is there a difference. The reason I ask for is because we had PTR zones setup through one hosting company. Upon doing a reverse DNS lookup by the IP it resolves to the domain the IP is pointing to. On the other hand we was testing another hosting providers service. They set the would setup the RDNS which they did. What's was odd is that the domain name had no PTR record placed in the DNS zone. That being said, every IP address would reverse into server.ourmaindomain.com (every IP). Do we need to have a PTR record setup on each DNZ zone to make sure they reverse uniquely into each domain?