In my earlier blog posts Building Hosted Exchange Part I (overview), Building Hosted Exchange Part II (Active Directory) and Building Hosted Exchange Part III (Exchange and ABP’s) and Building Hosted Exchange Part IV (Global Settings) we’ve created a simple Exchange 2010 organization that’s capable of hosting multiple organizations, separated from each other and each having their own Address Books. There’s one last issue I want to point out and that’s message routing. Exchange sees the entire Exchange organization as just one entity and does not care at all about routing between tenants. This is true for SMTP routing as well as out-of-office messages (which are SMTP messages as well of course) for internal and external OOF messages.
Note: using the Address Book Policies you can do ‘GAL segmentation’ but this is a feature that’s only targeted towards Address Books. Transport doesn’t do anything with Address Book Policies! Continue reading Building Hosted Exchange – Part V