Function peer_deny_names 

pub fn peer_deny_names(
    entry: &str,
    user: &str,
    match_fn: &impl Fn(&str, &str) -> bool,
) -> bool

Whether a deny entry names user.

A deny rule is checked with the caller’s own notion of identity and with a normalized comparison (leading @ stripped, ASCII case-insensitive). A blocklist errs toward denying, so matching a superset is the safe direction: the alternative admits a sender the operator wrote down.