I got this question via email yesterday – What is the reason to have an additional throttling policy in an environment that has Blackberry Server? The simple answer is – because of the client throttling policy introduced in Exchange 2010.
Let me explain. When Exchange 2010 gets installed, it configures a default client throttling policy. The intention of introducing the policy is to throttle the different type of client connections (OWA, ActiveSync, MAPI etc) when the limits (like number of active sessions) goes over the values specified in the policy. Get-ThrottlingPolicy gives you all the limits configured.
The value that we are interested in is RCAMaxConcurrency, which is set to 20 by default.
This means that a user can’t have more than 20 active sessions at a time. Because BlackBerry uses a single account (besadmin) to access all mailboxes & take care of mail flow to/from the blackberry handhelds, this limit of 20 sessions won’t allow Blackberry server to work properly.
Hence, we need to configure a new policy and change the RCAMaxConcurrency value to a much higher value & apply the policy only to the besadmin account. It is not recommended to edit the default policy, as it is applied to all users and defeats the client throttling process.
Hope this clears the confusion.