According to TID 7001460, at the bottom of the TID, I should be able to do a 'Find' of everything in the mailbox then mark all the messages as 'unread', then mark them as 'read' and it should fix the problem. I tried that but after doing a find of all messages, then marking them all, if I right click on a message, the option to mark the messages as 'read' or 'unread' is not there. I would prefer not to go through the long process of recreating the mailbox if it could be helped.

Any thoughts?