Exchange Server 2010 introduced a new feature called Client Throttling Policies. This feature is designed to allow administrators to enforce limits on client connections to the Exchange 2010 server over various protocols, with the goal of reducing the risk of a rogue client utilizing too many server resources. In other words, it is there to maintain Exchange server performance by preventing client connections from consuming all of the resources on the Exchange 2010 server.
In Exchange Server 2010 SP1 a client throttling policy is configured and enabled by default. This policy is reasonable for most client connectivity but can cause problems with Blackberry Enterprise Server, because the BES server makes all of its connections to BES user mailboxes as a single service account.
Initial advice from RIM (Blackberry) was to disable client throttling policies entirely. However that is not ideal because the throttling policies do have useful benefits for the performance of the Exchange 2010 environment.
Instead the current advice is to configure a client throttling policy specifically for the BES service account to allow it unlimited access to the Exchange 2010 server.
From the Exchange Management Shell run the following commands to create the throttling policy, configure the appropriate thresholds to unlimited, and assign the throttling policy to the mailbox used by the BES service account (in this example it is “BESAdmin”).
C:\> New-ThrottlingPolicy BESPolicy C:\> Set-ThrottlingPolicy BESPolicy -RCAMaxConcurrency $null -RCAPercentTimeInAD $null -RCAPercentTimeInCAS $null -RCAPercentTimeInMailboxRPC $null -EWSMaxConcurrency $null -EWSPercentTimeInAD $null -EWSPercentTimeInCAS $null -EWSPercentTimeInMailboxRPC $null -EWSMaxSubscriptions $null -EWSFastSearchTimeoutInSeconds $null -EWSFindCountLimit $null C:\> Set-Mailbox "BESAdmin" -ThrottlingPolicy BESPolicy
You can find these steps along with all of the preparation instructions for installing BES in an Exchange Server 2010 environment on the Blackberry documentation site.