ROlf,
There are two possible explanations here:
I) Your internet provider does not provide DHCP service, and the static IP you are assigning the e-smith server and gateway is not an IP provided by them - unlikely.
II) The "ETH1" interface is not your external interface, it is your internal interface. There are two ways to fix/verify this: in the e-smith console configuration screen, select "Swap ethernet assignments". Alternatively you can simply swap the ethernet cables at the back of you e-smith server and gateway.
Hope this helps,
Paul