An issue may exist where users cannot be added to the BlackBerry Enterprise Server from the BlackBerry Administration Service console in an environment that includes Microsoft Exchange 2010. When attempting to add users, they will not appear in the console when searched and cannot be added using the SMTP email address either.
The Microsoft Exchange 2010 SP1 Server in the organization does not include a public folder database and the BlackBerry Mail Store Service cannot connect to it. The BlackBerry Mail Store Service is designed to connect to the messaging servers in the organization's environment and retrieve the contact information that the BlackBerry Administration Service requires to search for user accounts.
BlackBerry service for existing users is not affected and they continue to operate normally.
There is a work around in order to fix that issue, please check the RIM article KB24470.
In another hand...check this RIM Compatibility Matrix for BES for Microsoft Exchange
The reference is for the KB mentioned earlier..
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