Function waited 

pub fn waited(
    items: &[Triaged],
    ledger: &Ledger,
    newsletters: bool,
    now: impl Fn(&Triaged) -> bool,
) -> Vec<Letter>

The mail that waited and may come now (now, as for sort): among the Porch’s messages (items), those waiting in the ledger, still unread and not set aside since (a sender blocked meanwhile).