The plugin is not really designed to forward an entire domain to another location, because there are far more efficient (and better) ways to do that - but if you need to for some reason or another, try using this in the redirect:
for the destination.
I am not entirely sure it will work, but you can try. If that does not work, then you will probably have to use something in the .htaccess file for the digital-media.be site (assuming you still have a WordPress site there and it is not just an alias). Search '.htaccess redirect one domain to another' on Google or Bing and you should be able to find an answer on how to achieve that with htaccess.
If you are not keeping a website at the digital-media.be site, then you should be able to just set a forward up on the domain through your host/domain panel - that is by far the simplest and best way to forward a domain.
Best of luck,