If you never double-click messages to open them, but instead always use the Reading Pane to do your work, Outlook will never mark the messages as read. To change this, go to Tools, Options, Other, and click Reading Pane. If you want messages to be marked as read if they are merely selected (that is, if the preview text shows up in the Reading Pane), click Mark Messages As Read In Preview Window. In the box below this line select the appropriate amount of time (in seconds) that you want Outlook to wait before it marks a message as read.