This article discusses the Google requirements of using Google Drive through a proxy server.
Applies to the following Sophos products
Sophos Web Appliance
What To Do
Google Drive can work though a proxy server but Google do not support authentication for their addresses. To allow Google Drive to work though your proxy server you must bypass authentication for the addresses contained in the Google article below.
As Google do not support NTLM or Kerberos authentication with Google Drive you will not be able to set user based rules for access the system. It is however possible to configure these rules by IP address on the Sophos Web Appliance.
If you are unable to use Google Drive after bypassing authentication for these domains then please contact Sophos Technical Support.