You configure a server that is running Microsoft Exchange Server 2010 Service Pack 2 (SP2) as a Client Access server (CAS).
The server that is running Exchange Server 2010 SP2 is used as a proxy to a server that is running Microsoft Exchange Server 2007.
You install Microsoft Exchange Server 2010 SP2 Update Rollup 1 (RU1) on the proxy server.
In this scenario, the proxy connection fails from the server that is running Exchange Server 2010 SP2 RU1 server to the server that is running Exchange Server 2007. And, you receive an error message that resembles the following:
Invalid user context cookie found in proxy response
Additionally, an event that resembles the following is logged in Event Viewer:
Event ID: 4999 Log Name: Application Source: MSExchange Common Task Category: General Level: Error Description: Watson report about to be sent for process id: 744, with parameters: E12, c-RTL-AMD64, 14.02.0283.003, OWA, M.E.Clients.Owa, M.E.C.O.C.ProxyUtilities.UpdateProxyUserContextIdFromResponse, M.E.C.O.Core.OwaAsyncOperationException, 413, 14.02.0283.003.
This issue occurs because of change to the user context cookie in Exchange Server 2010 SP2 RU1.
To resolve this issue, download and install Update Rollup 7 for Exchange Server 2007 SP3. For information about how to download and install Update Rollup 7 for Exchange Server 2007 SP3, visit the following Microsoft website: