Do you like using the Reading Pane but don’t like the fact that it marks an item Read? The fix is easy!
From the File tab in Outlook 2010, choose Advanced. In Outlook 2007, it’s Tools, Options and Other. In either version, click Reading Pane. You can select from several Reading Pane options. By default, “Mark items as read when viewed in the Reading Pane” is checked. Simply uncheck it.
Now, when you want an item marked Read, you can use the Ctrl+Q shortcut or the Unread/Read button in the Tags group on the Home tab.