Disable caching in IIS: in IIS Manager, go to Sites → 2X Web Server → Output Caching. Prevent caching on .aspx (see the installation manual for more info).
Provide your users with the following URL: http://WEB_SERVER_NAME/2XWebPortal/Logon.aspx.
Notice
Don't be tempted to set the site's default document to Logon.aspx. This breaks session management, resulting in your users to be able to log in but not start any application.