I'm getting ready to update my Exchange 2003 configuration to Exchange 2010. Going through the documentation, it seems that you install Exchange 2010 and join it to your current Exchange system Coexisting with your 2003 server, and then begin to move mailboxes over.
I am wondering how this process works exactly, specifically if there is any downtime required. The documentation isn't very clear as to whether or not this causes any downtime with your existing Exchange server. Basically, I'm wondering if I can install 2010 on my new server and bring it up into Coexistance mode with 2003 in a production environment without causing any downtime.