Windows Server 2008 R2 does not have GPO settings to force Windows 7 or any other Windows machines with Internet Explorer 9+ to go through the proxy with the usual Internet Explorer Maintenance option that forces proxy settings. Below are helpful articles on how to get this working with the new Group Policy Preferences within Server 2008 R2 registry settings:
- https://thommck.wordpress.com/2013/11/08/the-new-way-to-configure-internet-explorer-proxy-settings-with-group-policy/
- https://blogs.msdn.microsoft.com/askie/2015/10/12/how-to-configure-proxy-settings-for-ie10-and-ie11-as-iem-is-not-available/
- In this article, Case 2, Step 2 has worked in most cases.