You may have just seen my other question here.
One of the other things the client failed to tell me was that they also wanted a DAG between the U.S. and a site in Europe. I had never set up a DAG, but I did it, and opened a case with Microsoft to make sure I did it right. It seems fine, and everything replicates.
The problem is that when I attempted to test it failing over, it would not. I found information here that leads me to believe they may also need a hardware network load balancer, but I do not fully understand how it works, and how it makes Exchange understand that it has failed over. Could anyone explain that to me? I have looked.