We currently have two Forest: Forest A - AD 2003 - Has all the users (1000 plus) - and Exchange 2007 sp3 Forest B - AD 2008 - Has several application servers. Will be the future forest with Exchange 2010 SP1 We want to install Exchange 2010 SP1 in Forest B. However AD users are not scheduled to move to Forst B until later sometimes during 2012. What are the steps to install exchange 2010 sp1 in forest B, Sync the GALs between the two forests so I be able to move the mailboxes in group of 100. Based on what I have read, I believe I need to install FIM 2010. Not sure if I need to install FIM in both forests and what would be the best practice installation steps. Thank you