Smart Mailboxes - bug
I have tried to delete smart mailboxes and to add new ones over the last couple of weeks. I've been able to do this easily in the past. Every time I delete one or add one, the next time I restart the Mail app, the smart mail boxes reappear and my new ones vanish. I've tried everything, but can't see any way of stopping this. It's a fairly recent bug. I have the latest version of Big Sur 11.2.
MacBook Pro 15″, macOS 11.1