Publish Control Panel Email Settings in RDS

 You need to publish the following: c:\Windows\SysWOW64\control.exe mlcfg32.cpl

To do this in the Publish Applications wizard browse to Control.exe at the location shown above, and publish that, then go back in to the published app settings and modify;

1. General: Rename it to Email Settings.
2. Parameters: Select 'Always use the following command-line parameters' and enter this in the box: mlcfg32.cpl

Click OK and refresh RDWeb, you will see the new RemoteApp.