Have you tried looking at sys_email_log ? You can see the email linked to the notification and do some reporting from there, for example :
You can add dot walked fields from the email / event or notification table.
From there it's a matter of analyzing, which notifications are being sent more times (for example grouping on notification). And understanding further how they are triggered and how to reduce them, for example you can look at email digests:
Also consider understanding the concept of weight on a notification :
Notifications that have the same target table and recipients are considered duplicates if the weights are different. If weights are same, an additional evaluation is done to check if the subject and the body (excluding watermark) are same to qualify as duplicate notification. When there are duplicate notifications, the system only sends the notification with the highest weight. All other notifications are moved from the Outbox to the Skipped mailbox. The default value 0 causes the system to send the notification (assuming the conditions are met).
For example, suppose that a service desk agent adds a comment to an incident and shortly thereafter closes it. By default, these actions trigger both the Incident commented and Incident Closed notifications.
However, both notifications are from the Incident table and also notify the incident caller. The system only sends the notification with the highest weight, which in this case is the Incident Closed notification."
Docs here
Hope it helps
