At least with Mailgun, users who unsubscribe from reply notification emails also unsubscribe from password reset emails, and admins who unsubscribe also unsubscribe from backup download link emails. Because Mailgun stops sending any email to people who have unsubscribed. This is tricky.
I pretty much only want people to receive critical account-associated emails, or alternatively to be unable to unsubscribe from critical emails regardless if they unsubscribe from anything else. I must be missing something in the settings.