Need to create Domain but Web site with same name hosted by a third party?

I need to create a domain name without conflicting with an existing Web site (fst-llc). Existing Web site is based in Europe and currently manages our email accounts but now we are growing and opening a new office. I’m installing SBS 2008 so will be using exchange! My suggestion to use .Net was dismissed, users need same email address. Can I use .Local? What name will not create a conflict? Also, hate idea of forwarding emails to my exchange server. Ideally want to host .com @ new location but for now would be happy just to get thru the installation. Owner of fst-llc says I can use (or take) the .com name because is seems they don’t use the Web site at all??