Function update_account 

async fn update_account(
    account: &Account,
    password: &str,
    own: &[String],
    dirs: &Dirs,
    room: &dyn Fn(&Path) -> Option<u64>,
    progress: &mut dyn FnMut(&Progress),
    cancel: &Cancel,
    checker: Option<&Checker>,
    download: bool,
    update: &mut Update,
) -> Result<(), Stop>

An account’s download (download), its new messages checked as they come, then its messages kept without checks checked (check_kept).