You are part of a mixed Microsoft Exchange Server 2007 and Microsoft Exchange Server 2010 environment.
You have an Exchange Server 2010 server that has the Client Access server role installed.
You have an Exchange ActiveSync device that connects to the Exchange Server 2010 Client access server.
You synchronize the mailboxes between the device and an Exchange Server 2007 server.
In this scenario, the Exchange ActiveSync device cannot access the mailboxes. Additionally, the W3WP.exe process consumes excessive memory resources on the Exchange Server 2010 Client access server.
This issue occurs because the Exchange ActiveSync ProxyHandler unnecessarily creates proxy requests and waits for the requests to be completed. This behavior causes many proxy requests to time out, and then new requests are created.
To resolve this issue, install the following update rollup:
2582113 Description of Update Rollup 5 for Exchange Server 2010 Service Pack 1
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
For more information about Exchange ActiveSync, visit the following Microsoft website: