Before installing BES for multi-tenant Exchange 2010 SP1 /hosting you should read the following resources. You should also have deployed Exchange 2010 SP1 RU1.
This is a work in progress (so I don’t forget), so please check back for updates and corrections. Feel free to add comments or give me your experiences. There is also a forum running here, http://supportforums.blackberry.com/t5/BlackBerry-Enterprise-Server/Cross-organisation-user-search-exch-2010-sp1-hosted/m-p/659071#M7052.
BES 5.0.2 & Exchange 2010 SP1 RU1 /hosting:
BESX 5.0.2 & Exchange 2010 SP1 RU1 /hosting:
Post installation there are some other changes to make.
There is an additional step to configure BES 5.0.2 to work without public folders:
To restrict lookups follow this guidance:
You may also want to consider using LDAP instead of MAPI to lookup users, this will require a common attribute unique to users within each tenant organisation:
Using the above information, plus the standard installation guidance I have been able to install BES and add users.
Hopefully BES 5.0.3 will help us all out, maybe even an interim hotfix. I also recall that an MS update was required, but have a feeling this is included in Exchange 2010 SP1 RU1 - I could be wrong though.