# check_rcptto_exists Version 1.0 by Marc Sebastian Pelzer
#
# This plugin check wether a recipient of an incoming email exists in our local virtual-domains alias
# configuration file(s).
# The path to the alias file is hard-coded into this plug-in and you may need to modify it a bit in
# order to fit your set-up. Should not be a big problem if you know Perl :)
#
# You should create a config-file called "config/relayclients" which should contain a (maybe dynamically created)
# list of IP's or hostnames which are white-listed from this plug-in. It is recommended to put your relay-client's
# IP's inside this file, otherwise all outgoing connections will be rejected because the recipient of the outgoing
# mail is not locally known. 
#
# Fell free to change that behaviour as you like and to use this plug-in as an example for your own alias check.
#
use Qpsmtpd::DSN;
 
sub hook_rcpt {
 
  my ($self, $transaction, $recipient) = @_;
  my ($line, $user, $tmp);
 
  my $userExists = 0;
 
  my $remote_ip = $self->qp->connection->remote_ip;
  my $remote_host = $self->qp->connection->remote_host;
 
  # relayclients can send email to whoever thay want
  #
  my @relayclients = $self->qp->config("relayclients");
 
  foreach $tmp (@relayclients) {
 
    if ($remote_host =~ m!$tmp! || $remote_ip =~ m!$tmp!) {
 
        $self->log(LOGNOTICE, "Ok - remote peer is a allowed RELAY client ($remote_host / $remote_ip)");
        return DECLINED;
    }
  }
 
  return (DECLINED) unless $recipient->host && $recipient->user;
 
  my $host = lc $recipient->host;
  my $from = lc($recipient->user) . '@' . $host;
 
  unless (-e "/opt/local/exim/virtual-domains/$host") { return Qpsmtpd::DSN->no_such_user("mail to $from not accepted here"); }
 
  open (EXIM, "/opt/local/exim/virtual-domains/$host");
 
  while ($line = <EXIM>) {
 
    chomp($line);
 
    if ($line =~ m!^\s*\#! || $line =~ m!^\n$! || ! $line) { next; }
 
    ($user) = ($line =~ m!^\s*([^\:\s]+)\:!);
 
    if ($user && lc($user) eq lc($recipient->user)) { ++$userExists; }
  }
 
  close (EXIM);
 
  if ($userExists < 1) {
 
      $self->log(LOGNOTICE, "Recipient '$from' does not exists here. Slowing down spammer ...");
 
      sleep 60;     # slow down spammer
 
      return Qpsmtpd::DSN->no_such_user("mail to $from not accepted here");
  }
 
  $self->log(LOGNOTICE, "OK, recipient '$from' exists. Allowing to pass through ...");
 
  return (DECLINED);
}