DCs must be running Windows 2000 SP3 (or higher) or Windows Server 2003. GC servers should be placed in all sites/domains that host Exchange Server 2003. DNS servers must be configured correctly.
Run ForestPrep in the domain that hosts the forest's Schema Master. The account that runs ForestPrep must be a member of the Schema Admins and Enterprise Admins groups. Run DomainPrep in each domain that will utilize Exchange, even if no Exchange servers will actually be installed. The account that runs DomainPrep must be a member of the Domain Admins group. ForestPrep only needs to be run once. You must run both utilities at least once before installing Exchange Server 2003. When you run ForestPrep, specify a user account that will receive the Exchange Full Administrator permission.
