I am planning for a BES implementation and want to make sure I have things right. Any help would be appreciated!

My customer is going to implement BES, initially for 10 users but adding quickly to that. The 10 users are on multiple Exchange 2000 servers in 2 different Windows 2000 AD domains. I believe I will need a separate BES server for each AD domain but I just want to make sure. Any other considerations? Thanks!

EDIT: After some use of the search feature, I understand that if it was W2K3 AD and all domains were in the same forest it would work fine but it seems a little sketchy on whether this works with 2000 AD.