Function fetch_mail 

fn fetch_mail(config: &Config) -> bool

The inbox of each account fetched, every account at once (each in a thread of its own, as the window’s watchers fetch them: one connection each, the account’s lock across processes), what your spam filter moves moved, what your mail filters do done, its arrivals handed to the new-mail notifications, told in one notification once every account is fetched (mailnote::close_now), and to the home screen’s card when any came (homecard::mail_came); whether any came.