This document discusses transitioning and migrating to Microsoft Exchange Server 2007. It covers the different transition paths from previous versions of Exchange including upgrade, transition, and migration. It also discusses managing the interim mixed environment and moving mailboxes to Exchange Server 2007 using the Move-Mailbox commandlet. The document provides an agenda that reviews installing Exchange Server 2007 and then explores various transition scenarios such as single forest, cross forest, and resource forest transitions. It also discusses coexistence with Exchange Server 2003 and moving mailboxes between servers.