We're getting ready to install a brand-new Exchange Server 2003 organization; we also want to deploy Exchange 2003 Service Pack 1 (SP1). Can you tell me the correct order for running DomainPrep and ForestPrep in this type of situation?
This is one of those questions that gets more confusing the longer you think about it. On the surface, it wouldn't seem to matter whether you use SP1 or the Exchange 2003 release to manufacturing (RTM) version to perform the installation—except that the Exchange team doesn't make slipstreamed product install bits available. That means that you must first run ForestPrep using the Exchange 2003 RTM code, then run DomainPrep, using the RTM Setup version, in each affected domain. Then you have to install Exchange 2003. After you've done all this, you can use the Exchange 2003 SP1 update.exe tool to update the organization to SP1.
Don't be thrown off by the fact that update.exe will happily accept the /forestprep and /domainprep switches. When used with update.exe, these switches don't do anything. In any case, there aren't any schema changes specific to SP1. As a general rule, Microsoft tries to keep the number of schema updates at a minimum because many customers are (understandably) reluctant to make frequent schema updates (though Windows Server 2003 schema changes are less disruptive than those in Windows 2000).