Surf Soho - PPTP connection to Windows/Radius Server


I am trying to setup PPTP through a Peplink Surf Soho to a Windows server, but when I select > Remote User Access from the admin portal I can enable PPTP and select the WAN connection to listen on along with ‘untagged_LAN’ under the ‘connect to network section’ to allow my internal server to carry out DHCP.

But my question is, is there anyway to get through to the Radius Server running on the Microsoft server without having to put Local User Accounts onto the Router itself?