By default, Microsoft® Exchange 2010 limits the maximum number of connections from the BlackBerry® Enterprise Server to the Address Book service to 50. To permit the BlackBerry Enterprise Server to run, you must increase the number of permitted connections to a large value (for example, 100,000).

1. On the computer that hosts the Microsoft Exchange CAS server, in <drive>:\Program Files\Microsoft\Exchange Server\V14\Bin, in a text editor, open the microsoft.exchange.addressbook.service.exe.config file.
2. Change the value of the MaxSessionsPerUser key to 100000.
3. Save and close the file.
4. Restart the Address Book service.