Hello DuanYZ,
Thank you for posting in Microsoft community.
I did some research over the issue you are having, you may try to follow below steps to check the settings:
- Open Outlook and click on the "File" tab in the top left corner.
- Click on "Options" in the left-hand menu.
- In the Outlook Options window, click on "Mail" in the left-hand menu.
- Scroll down to the "Outlook panes" section and click on "Reading Pane".
- In the Reading Pane settings, you will see an option for "Single key reading using space bar". Uncheck this option.
- Click "OK" to save your changes. This should change the behavior of the delete key in Outlook so that it only deletes the immediate text, rather than the entire email.If you have any questions, please feel free to let me know. Thank you.
Best regards,
Trish - MSFT | Microsoft Community Support Specialist