We have domain Green and domain Red those are located in different forests and have trust relations. Both forests' schemas are prepared for Exchange Server 2007. There is an Exchange 2007 Organization in domain Green. Green Exchange admin just have logged-in from Red domain workstation and tries to create Exchange mailbox via Exchange Shell cmdlets: Enable-Mailbox -Identity 'green.com/Users/test4' -Alias 'test4' -Database 'CN=Mailbox Database,CN=First Storage Group,CN=InformationStore,CN=EX2K7,CN=Servers,CN=Exchange Administrative Group (FYDIBOHF23SPDLT),CN=Administrative Groups,CN=First 2007 Organization,CN=Microsoft Exchange,CN=Services,CN=Configuration,DC=green,DC=com' This cmdlet fails with error message: Active Directory dc.red.com is not available. If Green Exchange admin tries to do this from Green domain workstation, all works fine. What's wrong?

You need to specify -domaincontroller 'dc.green.com' grts, Kees