Exchange 2010 SP2 RU1 RU2 RU3 and CAS to CAS Proxy Incompatibility

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Exchange 2010 OWA

Exchange 2010 SP2 CAS Proxying

If any of you considering installing Exchnage 2010 SP2 with RU1 or RU2 or Ru3, the following information is addressed to you.


If your Exchange Organization have many Exchange Servers with CAS roles with different Exchange version, then after upgrade any of CAS server to Exchange 2010 SP2 with RU1 or RU2 or RU3 you can have problems with CAS to CAS proxying.

In scenario where an Exchange 2010 SP2 RU1 Client Access server is proxying to an earlier version of Exchange 2010 or Exchange 2007 Client Access server, then you are affected with a problem to use OWA.

In Event Log you can find errors like:

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.


Event ID: 136
Log Name: Application
Source: MSExchange OWA
Task Category: Proxy
Level: Error

The sign-in to Outlook Web App failed. User /o=xxxx/ou=xxx/cn=Recipients/cn=testuser has a mailbox on server version. However, no Client Access server or front-end server with a matching version was found to handle the request.

For users on Exchange 2007 and above, you can configure the Outlook Web Access URL for redirection using the externalURL parameter on the Exchange /owa virtual directory.


The SP2 RU1 package introduced a change to the user context cookie which is used in CAS to CAS proxying. This cousing a temporary incompatibility between SP2 RU1 or RU2 or RU3 servers and servers running earlier versions of Exchange. The change is such that earlier versions of Exchange do not understand the newer cookie used by the SP2 RUx server.

Below table show Exchange version compatibility in CAS proxying.

Update Exchange versions solves this problem.

Server proxy  Server being proxied to Solution
Exchange 2010 SP2 RU1 Any version of Exchange 2010 older than SP2 RU1 Apply Exchange 2010 SP2 RU2
Exchange 2010 SP2 RU1 Exchange 2007 Apply Exchange 2007 SP3 RU7
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