From Red Earth Software:
Policy Patrol Archiver stores Exchange e-mails into a central database, allowing you to apply e-mail retention policies and reduce the load on your Exchange Server. Users can search and restore their own messages through an easy-to-use web interface. Policy Patrol Archiver boosts Exchange Server performance by optionally stubbing messages, and removing messages from the Exchange Information Store. Policy Patrol Archiver allows you to set e-mail retention policies, specifying e-mails of a certain age to be automatically removed from the e-mail archive database.
Key Features: retrieve & restore e-mails through a web interface, advanced search functions allow for quick retrieval of relevant e-mails & attachments, database access based on Active Directory (AD) membership, single instance storage and compression to minimize database size, can stub messages or remove e-mails entirely to reduce Exchange Store size, automatically deletes e-mails according to retention policies, Audit Logging to trace searches and deletions from the database, export archived e-mails.