To add a field to the list of messages in a folder, first close the Reading Pane or widen the Message Listing Pane so that you see the items From, Subject, and Received in the header bar. (This bar is directly under the Inbox tag.) Then right-click the header bar and select Field Chooser (also accessible via the Advanced toolbar). A list of extra fields (including useful fields like Sensitivity, Cc, and Originator Reply Requested) will appear. Just click and drag them to the header bar to add them to the listing.