We run Exch 2k3 in native mode, and acquired a company running Exch 5.5. The companies will run independently in their own domains, but we need to have the ability to see each other's GAL. For example, in Outlook, we should have a GAL for Arkansas (Exch 5.5) and a GAL for Arizona (Exch 2k3). Also, this data should syncronize as users are added and removed. How do I make this happen with the least amount of upgrading?