Why doesn't macmail content display?
I have been opening and closing macmail to view the content in individual emails for two years. This is beyond inconvenient. Apple tech support has been zero help. I have tried countless fixes. Occasionally I will get a window that displays content. My recommendation to others with this problem, never close the working window. Hit the yellow button to hide it and call it back when needed. I realize everyone eventually has to restart, but this workaround is better than anything else I have discovered.
iMac 27″, macOS 10.15