Ah, daemon emails are a bit different. They're usually automated messages sent by a server's mail system.

If you get one, it might be because an email you sent couldn't be delivered for some reason. The "Mail Delivery Subsystem" or "MAILER-DAEMON" sends back a notification telling you there's been an issue.

So they're not about Bitcoin – just the internet's way of saying "Hey, your email didn't get through!"