I believe this has been requested before by someone but I can't find it so I am submitting a new feedback/request. It would be very useful if there was a setting for PI Notifications that would allow for sending emails to all subscribers on a notification rule in a single email instead of sending individual emails to each subscriber. For example, if there was a setting that would allow sending one email for a notification rule with all subscribers on the "TO" line that would allow users on the email notification to see who else received the alert and provide an easy way to "reply to all" if necessary to add information to the notification for all subscribers.
One workaround I remember seeing for this issue was to create Delivery Endpoint(s) and add all email subscribers to the delivery endpoint, then the delivery endpoint can be added as a subscriber to a notification rule and it would show all email recipients on one email. This technically works but adds a lot of management work to setup the delivery endpoints and add/remove users to them.