qpsmtpd/docs/advanced.md

Advanced Playground

Discarding messages

If you want to make the client think a message has been regularily accepted, but in real you delete it or send it to /dev/null, ..., use something like the following plugin and load it before your default queue plugin.

sub hook_queue {
  my ($self, $transaction) = @_;
  if ($transaction->notes('discard_mail')) {
    my $msg_id = $transaction->header->get('Message-Id') || '';
    $msg_id =~ s/[\r\n].*//s;
    return(OK, "Queued! $msg_id");
  }
  return(DECLINED);
}

Changing return values

This is an example how to use the isa_plugin method.

The rcpt_ok_maxrelay plugin wraps the rcpt_ok plugin. The rcpt_ok plugin checks the rcpthosts and morercpthosts config files for domains, which we accept mail for. If not found it tells the client that relaying is not allowed. Clients which are marked as relay clients are excluded from this rule. This plugin counts the number of unsuccessfull relaying attempts and drops the connection if too many were made.

The optional parameter MAX_RELAY_ATTEMPTS configures this plugin to drop the connection after MAX_RELAY_ATTEMPTS unsuccessful relaying attempts. Set to 0 to disable, default is 5.

Note: Do not load both (rcpt_ok and rcpt_ok_maxrelay). This plugin should be configured to run last, like rcpt_ok.

use Qpsmtpd::DSN;

sub init {
  my ($self, $qp, @args) = @_;
  die "too many arguments"
    if @args > 1;
  $self->{_count_relay_max} = defined $args[0] ? $args[0] : 5;
  $self->isa_plugin("rcpt_ok");
}

sub hook_rcpt {
  my ($self, $transaction, $recipient) = @_;
  my ($rc, @msg) = $self->SUPER::hook_rcpt($transaction, $recipient);

  return ($rc, @msg)
     unless (($rc == DENY) and $self->{_count_relay_max});

  my $count =
    ($self->connection->notes('count_relay_attempts') || 0) + 1;
  $self->connection->notes('count_relay_attempts', $count);

  return ($rc, @msg) unless ($count > $self->{_count_relay_max});
  return Qpsmtpd::DSN->relaying_denied(DENY_DISCONNECT,
          "Too many relaying attempts");
}

Results of other hooks

If we're in a transaction, the results of a callback are stored in

$self->transaction->notes($code->{name})->{"hook_$hook"}->{return}

If we're in a connection, store things in the connection notes instead.