Why am I still getting email notifications even after it has been marked as 'read' in my Outlook client?

Samsung Android devices using the default native email client.

The Email notification does not disappear automatically from the device and it is displayed on the Always On Display and in the notification bar, although the email has been marked as read in the Outlook Client.
The email notification disappears from the device only after opening the Email Client within the Knox Workspace.

This is 'as designed' behavior. New mail notification are cleared only after the email app is opened.