I don't want unknown users to be able to create support issues. I also don't want those issues created from incoming mail.
This is all fairly easy to set up, and we have this working.
However, what I want to know: Can I have a notification sent to the sender of an email when his email address is not known?
Something like: "We don't recognize your emailaddress, that is why no support issue is created. If you believe you are entitled to support, please do the following.... <referring to other channels>"
