Enable Notification Tracking - for Troubleshooting Purposes Only

Hello everyone,

Enable Notification Tracking - for Troubleshooting Purposes Only - this allows users to see notifications that may have failed, such as when a candidate fails to provide an email or phone number for the notification to deliver

When you add a candidate to a requisition, an invitation email will be sent to the candidate asking them to apply to the requisition, so I did enable Enable Notification Tracking - for Troubleshooting Purposes Only feature and added a candidate to a requisition who does NOT have an email address updated, that means this notification has been failed, but where can I see this notification failed thing? Where's it being captured?