This is a combo Networking/AD/Exchange question but seems like it probably fits here.
We recently acquired 2 additional companys that also have their own forest/domains and Exchange 2K Servers. They are now linked via T1's.
What is the best practice for replicating Exchange calendar information ONLY between the 3 Exchange servers. Trusts are enabled but currently no AD information is being replicated between the forests. From my understanding Routing group and Bridgehead servers now require you to integrate AD. I would rather not integrate the entire AD structure if I do not have to because of previous experiences with AD corruption.