I am adding an Exchange 2010 server to our Exchange 2003 environment. We are a small shop so the transport server etc will run on the 2010 server like the 2003 servers. My question is after I install 2010 will my domain admins lose the taps in ADUC such as exchange permissions etc when administrating users on Exchange 2003? I plan on migrating users but not all at once can this be done with minimal impact to production or is it install 2010 and upgrade all mailboxes? Thank you, John Dunn