Seriously, with Full Screen Messages

Stopped using Outlook a year ago over the fact that when you click on a message it only opens about a quarter of the screen. Thought by now it would be fixed. What gives? Don't want to go back to old Outlook on PC as it's slow and hangs in the background and you have to kill it in Task Manager all the time. Any fixes for getting messages to open full screen? Appreciate any ideas and thoughts.