When you set the number of rings for the auto-answer in Routing and Remote Access Server (RRAS) to zero, it does not work. For additional information, see the following article or articles in the Microsoft Knowledge Base:

Fixes an issue in which a user cannot sign in by using a mobile device in a Lync Server 2010 environment that has Mobility Service deployed. This issue occurs after Mobility Service encounters an unhandled exception.

When it is fetching an FTP file without a file name extension, Proxy Server 2.0 does not separate the HTTP headers from the data with a blank line as it should. Because of this, the browser cannot determine where the header ends and truncates the data...