qpsmtpd/plugins/check_badrcptto

# this plugin checks the badrcptto config (like badmailfrom, but for rcpt address
# rather than sender address)
use Qpsmtpd::DSN;

sub hook_rcpt {
  my ($self, $transaction, $recipient, %param) = @_;
  my @badrcptto = $self->qp->config("badrcptto") or return (DECLINED);
  return (DECLINED) unless $recipient->host && $recipient->user;
  my $host = lc $recipient->host;
  my $to = lc($recipient->user) . '@' . $host;
  for my $bad (@badrcptto) {
    $bad = lc $bad;
    $bad =~ s/^\s*(\S+)/$1/;
    return Qpsmtpd::DSN->no_such_user("mail to $bad not accepted here")
      if $bad eq $to;
    return Qpsmtpd::DSN->no_such_user("mail to $bad not accepted here")
      if substr($bad,0,1) eq '@' && $bad eq "\@$host";
  }
  return (DECLINED);
}