Originally Posted by robertlouwen
webmail.something.nu gives forbidden and webmail.something.org gives not found
Well because it is not 100% necessary ( something.x/webmail works ! )
I want to thank you for your time and effort.
Are you 100% sure you set up the subdomain correctly?
It works on debian with ispc3 and the plugin for me.
Have you edited the Main site (the one you created the subdomain for)? This is necessary, because the new plugin creates the symlinks only on update of the main site data. you can check if a symlink is present in the web directory of the website.