[Admiral]

Тогда пробуем рецепт от самой МикроСофт
How to deploy an SSTP-based VPN server behind a SSL load balancer in Windows Server 2008
Make a Virtual Private Network (VPN) Connection
RRAS Server
Так же можно подправить сертификат How to change the computer certificate on a Windows Server 2008-based computer that is running the "Routing and Remote Access" service and SSTP