You won't see them in the preview pane, but if you OPEN a message you will see them on the toolbar. You may see a list of emails that you can scroll through. I have turned that feature off as it doesn't work for me
You can also add buttons to the tool bar such as delete and next and delete and previous. Right click on the tool bar and click CUSTOMIZE where you can add commands from the daunting list and assign them icons if you wish

Although this is a bad idea, you could delete all the menus and toolbar elements then rebuild them by hand. Again that would not be a good idea but it shows you how customizable this program is