I've got weird things going on with my Apple mail (which I use across a Mac, iPhone and iPad). Â I'm seeing things I've never looked at already appearing 'read'. Â It doesn't seem to be a sorting issue (apple intelligence driven 'priority messages' etc),Â
Change your password and restart all your devices.
I know nothing of Apple, but that sounds like you've left something open somewhere that you've forgotten about, or an app playing silly buggers maybe. Forcibly terminating extant connections should sort it out I think. Â
Using the Mail app on a Mac rebuild the mailbox(es) first (select Mailbox in menubar and Rebuild is the last option). Occassionally my machines show messages that I can't delete as they're all ready gone from one of the other devices
I second trying a rebuild.Â