I'm getting a little bit resigned about how things work.
Yes, I'm logged as the super admin.
The list_items() function is commented to be sure it works with default settings.
After reading your post I have tried with this:
public function list…
And one more thing:
1. how to send a message also to the sender's email as a confirmation of sent email?
2. how to put sender's email as the "from" field in the incoming email?