We have released security updates for the following versions of Exchange:
Security Update for Exchange 2000 Server (KB976703)
Security Update for Exchange Server 2003 Service Pack 2 (KB976702)
Update Rollup 10 for Exchange Server 2007 Service Pack 1 (KB981407)
Update Rollup 4 for Exchange Server 2007 Service Pack 2 (KB981383)
Update Rollup 3 for Exchange Server 2010 (KB981401)
Security related changes for Exchange 2007 and Exchange 2010 ship as Update rollups following the cumulative servicing model. However we have tried to keep the number of non-security related changes in these rollups down to a minimum.