Outlook 2016 - Do not mark messages as read until you double-click an email to open it

  1. Open Outlook
  2. Click File in the top left
  3. Click Options
  4. On the left, click Advanced, then on the right, click Reading Pane...
  5. Un-check 'Mark items as read when viewed in the Reading Pane' and un-check 'Mark item as read when selection changes'