Hello All,
I currently have a requirement to add one of our channel island offices to our BES server and was wondering what would be required - here are my thoughts..

They have their own forest and domain, so do I need;

A one way trust (we curently trust them)
The BES account from our domain to have permissions on their Exchange server?
And obviously add their exchange accounts to our BES server?

Would that be enough for me to add their users to our BES server enabling them to use our resources?

All help/ideas welcomed,

Regards,
Shaun

While Not supported, you will at least need a new BES instance with a different Service account accessing the second Exchange Organization. You will still need the forest trusts to get from one forest to the other.
I haven't tried it in a while, but the only issue you may find is the mapi service not being able to connect to the two exchange organizations at the same time.

Hope this helps