I’ve tried this but, sadly it won’t work out because of Category not accepting "anonymous email" from known users - #28 by Simon_Manning
That would be nice. It is hard to explain to our users, that if they using mailing list mode is more a mailinglist-ish mode 
Even some won’t switch from our Mailman mailinglist, so for now we have two systems running but would like to switch to discourse absolutely.
We were very inspired by your use case, but we don’t have just one support group but a couple of them that’s why we need those permission regulations.
Thank you for your replies
cincerly bren