I don't use Outlook, so I can't speak from experience, but in Thunderbird, if I right click anywhere in the toolbar area, either in the program or an email it lists the toolbars. I can uncheck a toolbar and it is no longer displayed, check it again and it is displayed.
Are there any email display settings in the main Outlook program ?
I have an Options setting in the Thunderbird program and that has rudimentary Read and Display settings, perhaps Outlook has something similar.