OSX High Sierra - Mail thread display issues
Whenever I have a multi-message thread in Mail, the display goes black. This only happens when there are multiple messages.
Mac mini, macOS High Sierra (10.13)
Is this classic view? If yes, try unchecking Classic in Mail > Preferences > Viewing.
You might have to adjust the columns to view the message window.
I believe this is a bug in Mail at this time. Hopefully Apple will fix in 10.13.1. If enough people send feedback, it may get the problem/suggested change solved sooner.