There needs to be a quick way or setting to as I read the emails that, well, they leave the unread box. Immediately.
The only way to clear the read mails from the Unread global folder is to “click to another folder and then click back to the Unread folder”.
The reason for this as @gary advised previously in the below thread, is if the emails automatically removed from the unread global folder after being read “where alot of users have already suggested that”, it would then create a cascade effect and would eventually clear all your unread messages.
So that’s why read messages don’t automatically clear. That may change one-day if there is a way to avoid the cascading auto read effect.