I last used Exchange Server in a production environment on the 2003 SMB server, but really most of my experience is with Exchange 4.0, 5.5. and 2000 in Enterprises.
Why so old? Because back then, it was pretty awful compared to Notes. So I picked Notes, which gave me over a decade of work. Not a bad choice, I think...
Anyway, here's the first reactions to the course.
So many prerequisites!