Wow.
After an update, I now cannot allow Kmail to run because it creates empty messages in my Gmail account constantly. There were a zillion kf5-* packages updated, so I have no idea what got updated that I should try to find a downgrade for.
This bug:
https://bugs.kde.org/show_bug.cgi?id=348103
seems to match my problem.
Has anyone else seen this? Or am I the only user still using Kmail?