By default, Microsoft® Exchange 2010 uses client throttling policies to track the bandwidth that each Microsoft Exchange user
consumes and enforce bandwidth limits, as necessary. The policies affect the performance of the BlackBerry® Enterprise Server
negatively, so you should turn off client throttling for the Windows® account that has a Microsoft Exchange mailbox.
Please check KB20608-Random BlackBerry smartphones fail to start and "MAPIMailbox - OpenMsgStore (0x8004011d) failed" appears in BlackBerry Messaging Agent and Application logs due to Microsoft Exchange 2010 Throttling Policy