Using classic Outlook for Windows in business environments
I came across another thread that said the following:
"To work around this issue, you can disable the Reading Pane.
- On the People pane select View, then Reading Pane, and set to Off.
- If the View menu is covered, click Alt + Space Bar, and then select Restore. This will get you back to the minimized state and you can now do the Reading Pane change in Step 1.