In Exchange 2010, Microsoft introduced the ability to perform discovery searches across an Exchange 2010 organization using Multi-Mailbox Search. Along with Personal Archives, which allows you to eliminate the risk from PST files and store historical messaging data in Exchange; Legal Hold, which allows you to preserve data for eDiscovery, and Retention Policies, which allow you to manage email lifecycle, it has been one of the most popular features of Exchange 2010.
Multi-Mailbox Search used to require an Enterprise Client Access License for each mailbox searched. Now, Microsoft has changed this and an Enterprise CAL for Multi-Mailbox Search is no longer required!
