Mac Mail preferences shows only blank "Fonts and Colors" window

This question has been asked before and the answer offered — to boot in safe mode in order to clear out caches — does not work. I have found the real solution to restore access to my preferences:

• quit mail
• Delete "com.apple.mail.plist" in the folder "Library/Containers/com.apple.mail/Data/Library/Preferences"
• Restart mail. You will have to reset previous customization preferences.

Hope this helps someone else.