OK, I am setting up a new environment for a client. I have installed Server 2008 R2 as a DC on one server, and Server 2008 SP2 (after I found out that I couldn't install Exchange 2007 SP1 on a R2 2008 Server) and Exchange 2007 SP1 on another server. I am rebuilding the AD by hand (fairly small). I had about half of the users and groups created in AD when I went ahead and built the Exchange Server. If I understand correctly, Exchange 2007 runs the schema prep automatically, and after I installed, I did see the Exchange Security Groups in AD, however, I cannot get any of my existing AD users mail enabled, and any new users that I create do not have any Exchange attributes associated. I ran the schema prep manually as well just in case. Any ideas what I am missing?