issue in email notifications
3 answers
If a user gets a mail or not depends on their personal mail notification settings. There is no enforcement to send mail to all users.
There is no documented feature that a response to the notification mail does anything. Best case it gets stuck in the inbox of the technical user account that is used to send the e-mail - which is easy enough to see in the notification. It should probably be configured as a no-response account.
If you want a different functionality, you would have to set up and develop it on your own.