I use a hosting service for a web site, I have the domain name registered with Verio. I created another domain name from another registrar that I wanted to point to the same website. When I hosted my own webserver this was simply a matter of pointing the registrars NS setting to my DNS server and adding another A record. Piece of cake.
With this third party hosting I have to change the DNS on their server using an applet. When I add another A record using the same IP it "stacks" it on top of the first one. i.e. NewDomainName.com.OldDomainName.com all as one entry.
Why does this happen?