Hi ! This is Benpella . I'm a fellow Outlook.com user and I'm sorry to hear about the issue.
If the reading pane in Outlook keeps switching on or off, it could be due to a configuration setting or a glitch in the software. Here are some troubleshooting steps you can try:
Adjust Reading Pane Settings: In Outlook, go to the "View" tab and click on "Reading Pane." From the drop-down menu, select the desired reading pane option, such as "Right," "Bottom," or "Off." Make sure the desired reading pane option is selected and see if the issue persists.
Reset Reading Pane Settings: If adjusting the settings didn't resolve the issue, you can try resetting the reading pane settings. Go to the "View" tab and click on "Reading Pane." From the drop-down menu, select "Off." Then restart Outlook and go back to the "Reading Pane" settings to choose your preferred option again.
Check Layout Options: Outlook also has layout options that can affect the reading pane. Go to the "View" tab and click on "Layout" or "Layout Options." Ensure that the desired layout option is selected, such as "Message Preview" or "AutoPreview." Experiment with different layout options to see if it resolves the issue.
Repair Outlook: If the problem persists, it may be worth running the built-in repair feature of Outlook. Close Outlook and navigate to the Control Panel (in Windows) or System Preferences (on Mac). Look for the "Programs" or "Applications" section and find Microsoft Office/Outlook. Choose the option to repair or uninstall the software. Follow the on-screen instructions to repair Outlook.
Update Outlook: Ensure that you have the latest updates for Outlook installed. Updates often include bug fixes and improvements that can address known issues. Open Outlook and go to the "File" tab. Select "Office Account" (or a similar option) and click on "Update Options." Choose "Update Now" to check for and install any available updates.
Best regards
Benpella