The background on my emails turned black. How do I change it back

Mail > Preferences > Viewing > uncheck: Use dark background for messages

garyo1952 wrote:

How do I change the email message background back to white? It has suddenly changed to black.

How to use Dark Mode on your Mac - Apple Support

Dark mode has to be enabled to get the chk box in Mail>Preferences

even then you may or may not have a dark background—flip a few switches

Apple Feedback http://www.apple.com/feedback

Feedback assistant to file bug reports: https://feedbackassistant.apple.com/welcome