If I understand this correctly (and please correct me if I am wrong) reverse DNS works by trying to match an IP address to a domain name, rather than the domain name to the IP address. But how does this work if a single IP address has multiple Domain names associated with it? for instance we host a mail server which has about 35 different domains associated with it. Does a reverse DNS entry have to be made for each domain all associating it with that servers IP address? and if so will the reverse DNS then just pull a list of associated domain names and then match the sending domain to that?