You will have to run a script to change the status.

Hi We Do Software 

Thank you for your response, much appreciated. 

Yes, agreed 100% - I managed to find a fast & effective method of clearing the errored mail notifications by utilizing 300 People's Scheduled Task functionality to run a SQL Query/Script. 

**********************************************************************************************************************************************************************

Solution Steps:

1. Navigate to Scheduler > Scheduled Tasks and click on the 'New' button from the ribbon.

2. Populate all mandatory & required fields:

• Select 'SQL - Scheduled SQL Query' as the 'Scheduled Task Type'
• Type a title in the 'Schedule Name' field. (e.g. SQL Query to clear Errored Mail Notifications)
• Click on the 'Recurrence Info' button next to the 'Next Run Time' field and configure as required.
• Paste the following SQL query into the 'Scheduled SQL Query' field toward the bottom of the screen: 
  

3. Click on the 'Save' button from the ribbon.

4) Click on the 'Run Now' button from the ribbon and wait for the task to finish running.
(Progress can be checked by navigating to the 'Instance History' screen and frequently clicking on the 'Refresh' button.)

5) When the 'Instance Status' reflects as 'D - Done', navigate to Utilities > Mail Notifications to confirm that all errored mail notifications have been cleared.

6) Return to Landing Page/Home Screen and click on the System Health's 'Refresh' button to resolve the warning.