No messages coming from the support server are in spam.
I changed the webmaster email address from "[email protected]" to "[email protected]" and ... the notification messages are sent and received.
Change back the webmaster user email address to "[email protected]" stopped again the notification messages reception.
It is a very strange situation because the "[email protected]" address is receiving many others email messages.
Many thanks Kasia, You correctly understood the desired feature.
I wanted to implement it in a easy (and not very professional) way. I was not asking for the lines of code but instead if there is documentation or some easy "API" or some knowledge about the point of intersection to inject those three or four lines of code without study the entire plugin code.
If no ... it is ok to me move the question to Features & Feedback section. We can wait.