Mail Preferences Won't Open
I have the latest MacBook Air but am unable to access Mail Preferences.
When I click on "Mail" and then "Preferences" it will only open a blank "Rules" window and nothing else. I have force-quit Mail and rebooted the Mac but it still won't open the full Preferences window that should show "General", "Accounts", "Signatures" etc.
Can anyone help... Please?
MacBook Air 13", macOS 10.14