Strange DNS issue

I'm trying to get NetFlix US working using a US DNS service. However, it doesn't work with my Astaro box in the network.
Under "DNS" settings and "Forwarders" I have unchecked the "Use forwarders assigned by ISP" box and the main box is empty.
It's like Astaro is handling DNS for everything which passes through it even if that PC happens to have manually defined a different DNS server.
Can anyone help?

Additional info:

Home user
ASG 7
Setup: Network --> ASG --> Internet
I can enter the US DNS server into "DNS Forwarders" and it works, but then everything on the network is using it, and that's not something I want.