If you delete the message you are looking at, Thunderbird has to display something. A blank white screen would not be very helpful. There are some settings you can change - check options/preferences - display - advanced. (Illustrated here https://blog.programster.org/thunderbird-stop-opening-next-message) What you see also may depend on the view layout you are using - whether preview pane is on and suchlike. More info here https://support.mozilla.org/en-US/kb/how-change-thunderbird-layout Try adjusting some of those until you find a setup you like.

Try this add-on: https://addons.thunderbird.net/en-US/thunderbird/addon/deselect-on-delete-tb78/ https://support.mozilla.org/en-US/kb/installing-addon-thunderbird