"HTTP Error 400 Bad Request" error message when you use OWA to log on to a newly created Exchange Server 2007 mailbox

Symptoms

Consider the following scenario:

In a mixed Microsoft Exchange Server 2010 and Microsoft Exchange Server 2007 environment, an Exchange Server 2010 Client Access server handles the proxy requests for the Exchange Server 2007 Client Access server.
You create a new mailbox on an Exchange Server 2007 server.
You log on to this mailbox by using Outlook Web App (OWA).

Note�This is the first time that you log on to this mailbox.
You are automatically routed to the language selection page in OWA.
You select a language, and then you click the�OK�button.

In this scenario, you receive the following error message:

HTTP Error 400 Bad Request

To resolve this issue, install the following update rollup:

2509911� Description of Update Rollup 4 for Exchange Server 2007 Service Pack 3

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

For more information about Proxying and Redirection, visit the following Microsoft website:

Keywords: KB2484147, kbsurveynew, kbexpertiseinter, kbhotfixrollup, kbfix, kbqfe

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