A. No. You can't introduce Exchange 2007 into an existing Exchange organization while an Exchange 5.5 server still exists in the organization. If you run Exchange 5.5, you must first upgrade to Exchange 2000 Server or Exchange Server 2003, effectively Exchange native mode. After you move the mailboxes to an Exchange 2000 or Exchange 2003 organization, you can move the mailboxes to Exchange 2007 via the Exchange 2007 GUI if Exchange 2007 and the Exchange 2003/2000 installation are in the same organization or by using the Power Shell Move-Mailbox command for cross-organization migrations.