sub register {
  my ($self, $qp) = @_;
  $self->register_hook("mail", "mail_handler");
  $self->register_hook("rcpt", "rcpt_handler");
}

sub mail_handler {
  my ($self, $transaction, $sender) = @_;
  # lookup the address here; but always just return DECLINED
  if ($sender->format ne "<>" and $self->qp->config('rhsbl_zones')) {
    my %rhsbl_zones = map { (split /\s+/, $_, 2)[0,1] } $self->qp->config('rhsbl_zones');
    my $host = $sender->host;
    for my $rhsbl (keys %rhsbl_zones) {
      $transaction->notes('rhsbl', "Mail from $host rejected because it $rhsbl_zones{$rhsbl}")
	if check_rhsbl($self, $rhsbl, $host);
    }
  }
}

sub rcpt_handler {
  my ($self, $transaction, $rcpt) = @_;
  my $note = $transaction->notes('rhsbl');
  return (DENY, $note) if $note;
  return DECLINED;
}

sub check_rhsbl {
  my ($self, $rhsbl, $host) = @_;
  return 0 unless $host;
  $self->log(2, "checking $host in $rhsbl");
  return 1 if ((gethostbyname("$host.$rhsbl"))[4]);
  return 0;
}