I see that a 'Read' column can be added from the Field Chooser to a folder view, but Outlook cannot sort by this column. In Outlook on my PC, I can click on Filter E-mail Unread, or Search Unread, both of which set the search parameter to 'read:no' and thereby display only unread messages in any view.
Flagging a message causes erratic behavior in viewing the To Do List, with nothing showing under Today except a lot of blank entries.