Mail: "Mark as Read"
Change how "Mark as Read" works...
If one selects a mail in Outlook that has not previously been read you will be presented to the mail content and you can/will read it. So it is read.
Now if you right click on it, the "Mark as read" is presented. Why - it is already read.
Now if you un-select the particular mail and select the same again, the "Mark as Unread" is presented as an option.
So the very common use-case "Look at mail body, realize mail is important, want to mark it as unread" require and extra un-select / select action.
Suggestion: Once a mail has been selected, make the contextual rigth-click option to say "Mark as unread". This is logical as indeed I have in fact read the mail.
If an unread mail is in a different folder rather than the inbox, Outlook marks it first as read when it is being viewed in the reading pane. And, it marks it unread after the sync with the server. Never marks it as read again.