After you apply Microsoft Exchange Server 2010 Service Pack 2 (SP2), users cannot connect to Microsoft Outlook Web App by using the HTTP protocol. This problem occurs even if you disable the "Require secure channel (SSL)" option in the Outlook Web App virtual directory.
This problem occurs because Exchange Server 2010 SP2 uses the HTTPS protocol to connect to Outlook Web App.
To work around this problem, follow these steps:
In the Client Access Server (CAS) server that hosts the Outlook Web App, open the Web.config file by using Notepad. By default, the Web.config file is installed in the following location: