qpsmtpd/plugins/check_relay

# this plugin checks the standard rcpthosts config and
# $ENV{RELAYCLIENT} to see if relaying is allowed.
#
# It should be configured to be run _LAST_!
#

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

sub check_relay {
  my ($self, $transaction, $recipient) = @_;
  my $host = lc $recipient->host;

  my @rcpt_hosts = ($self->qp->config("me"), $self->qp->config("rcpthosts"));
  
  # Allow 'no @' addresses for 'postmaster' and 'abuse'
  # qmail-smtpd will do this for all users without a domain, but we'll
  # be a bit more picky.  Maybe that's a bad idea.
  my $user = $recipient->user;
  $host = $self->qp->config("me")
    if ($host eq "" && (lc $user eq "postmaster" || lc $user eq "abuse"));

  return (OK) if exists $ENV{RELAYCLIENT};
  for my $allowed (@rcpt_hosts) {
    $allowed =~ s/^\s*(\S+)/$1/;
    return (OK) if $host eq lc $allowed;
    return (OK) if substr($allowed,0,1) eq "." and $host =~ m/\Q$allowed\E$/i;
  }
  return (DENY);
}