Have Outlook Show the First Message in Your Reading Pane (Preview Pane).

Posted on September 29, 2014October 1, 2014 by Jeff Feiertag

Click the gear symbol at the top-right of the screen.
Choose Display Settings. The Message List options will load by default.
Click Reading Pane.
Choose Select the First Message in the List from the On Sign-In.
Click the OK button above the options.