Throughout my years of working IT I have come across some very unique user setups in Outlook. Some users will tweak every thing to the point it is barely useable, at least if you’re not familiar with how they set it up. If you need to use a co workers computer or a “spare’ while you’re waiting on IT to fix your machine, here is an easy way to at least get the reading pane familiar.
In Outlook click on View Reading Pane Right, Bottom, or Off
That is all there is to it. Now you can go through the rest of the toolbar options to customize everything else!