The Solution to my problem was:
To add this to .htacces in my webroot folder /httpdocs/.htaccess
This will cause all non-existing domains to end op in root folder where they are picked up by the .htaccess. (no symbolic links anymore)
# Enable Rewrite Engine
RewriteEngine on
# Rewrite all non-existing domains to example.com
RewriteCond %{HTTP_HOST} !example\.com$ [NC] #just add your main domain here
RewriteRule ^.*$ http://www.example.com%{REQUEST_URI} [R=301,L]