My company is running a mixed Windows 2000/Windows NT environment with one Exchange Server 5.5/Win2K server. Can I install Exchange 2000 Server and join the current site for testing, without affecting the existing environment?
As soon as you install Exchange 2000, you modify the Active Directory (AD) schema, and schema modifications are permanent. Adding any kind of Exchange server to an existing site modifies information in the Exchange 5.5 directory as well, although those changes are reversible. The best way to avoid affecting your existing environment is to create a parallel Win2K forest and install Exchange 2000 in it. The closer this environment is to your production environment, the more value you'll get from it as a test environment.