You cannot log on to OWA when a proxy is set up in an Exchange Server 2010 environment
Content provided by Microsoft
Applies to: Microsoft Exchange Server 2010 Service Pack 2Exchange Server 2010 EnterpriseExchange Server 2010 Standard
Assume that you apply Update Rollup 1 for Microsoft Exchange Server 2010 Service Pack 2 on an Exchange Server 2010 Client Access server. The Exchange Server 2010 Client Access server acts as a proxy server for an Exchange Server 2007 Client Access server that is not connected to the Internet. When a user tries to log on to Outlook Web App (OWA) in this situation, the logon attempt fails. Additionally, you receive an error message that states that an exception was thrown on the proxy server.
Note This issue may also occur when the proxy is set up between Exchange Server 2010 Client Access servers, and not all the servers are updated.
This issue occurs because the proxy server tries to parse and validate a canary that does not match the expected format. Therefore, an exception is thrown.
To resolve this issue, install the following update rollup:
2661854 Description of Update Rollup 2 for Exchange Server 2010 Service Pack 2
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
For more information about proxy servers and redirection in an Exchange Server 2010 organization, visit the following Microsoft website: