An EWS application that runs on behalf of a user quickly consumes resources on the Microsoft Exchange server 2010. When we investigated, we noticed that the EWS operations the application performs exceed the limit that is set in the client throttling policies. As we know that the client throttling policies for Exchange Web Service are enabled in a Microsoft Exchange Server 2010 environment – all client throttling policies are enabled in Microsoft Exchange Server 2010 Service Pack 1 (SP1) or in Microsoft Exchange Server 2010 Service Pack 2 (SP2), by default. In this scenario, all the EWS applications that run on behalf of the user are throttled unexpectedly. The expected behavior is that only the EWS application whose operations exceed the limit that is set in the client throttling policies is restricted.
This issue occurs because all the EWS applications that run on behalf of the user consume the same client throttling policy budget. To resolve the problem, first make sure you installed the latest service pack & rollup for Exchange Server 2010 or install the Update Rollup 4 for Exchange Server 2010 Service Pack 2. You can refer: http://support.microsoft.com/kb/2706690