Yesterday afternoon my mail app suddenly decided that I no longer wanted the reading pane off to the right side unless I am in full screen mode. If I open the window wider (but not full screen) it will either let me have the preview screen or the bar off to the left with the list of accounts, but not both. If I open the mail app in full screen it has both the preview pane and the ribbon on the left.
I'm sure I must have clicked something to make it do this but have no idea what. I've clicked and unclicked "show preview text" a few times and completely restarted once to no avail. What have I done and how do I fix it? I'm using a desktop PC.