To move objects within the same domain, open the Microsoft Management Console (MMC) Active Directory Users and Computers snap-in (go to Start, Programs, Administrative Tools, and click Active Directory Users and Computers), right-click the object, then select Move from the context menu (or in Windows Server 2003, you can simply drag objects to their new location). Unfortunately, you can't use the snap-in to move objects between domains.

Exchange relies heavily on Active Directory (AD) and uses several services to optimize AD communication. One of these services is the DSAccess service, which provides a cache of information from AD to various Exchange components, including the Information Store (IS), the Message Transfer Agent (MTA), and any other component that requires AD information. By recovering cached AD information, Exchange requires fewer direct queries to the DCs