[Mimedefang] Problems with outgoing bounce messages, unkown user, plus to many bad files in sendmail queue

[An.H.Nguyen]

I've got many spam emails sent from non existing senders to unkown users and 
do not want to generate bounce messages.
All files in sendmail queue was removed on Friday and now (Tuesday) I have 
800+ bounce messages in the queue. Plus, why do I have 9000+ files in the 
sendmail queue now?
I hope Mimedefang can help reducing the problem but I am new to it.
Have I missed anything here? The manual smtp tests indicates that it can 
validate recipient users, but many bounce messages still got created (by 
localhost (localhost)) and stuck in the queue.

Please advise! Thank You (:
Below you'll find my filter code and the manual smtp session output and one 
of the bounce message headers (note that I replaced the actual server with 
mimedefang_server and similarly for user at dom.com)

sub filter_recipient
{
      my($recip, $sender, $ip, $host, $first, $helo, $rcpt_mailer,
$rcpt_host, $rcpt_addr) = @_;

      my $relay = undef;
      $relay = "internal_server" if ($recip =~ m/\@domain\.com$/i);
      if ($relay)
      {
              return md_check_against_smtp_server($sender, $recip,
"mimedefang_server", $relay);
      }

      return('CONTINUE', "OK");  # accept recipient if dont find relay
}


c:\telnet mimedefang_server 25
220 ESMTP Mailer Ready
helo a.abc.com
250 mimedefang_server Hello client_host [x.x.x.x], pleased to meet you
mail from:a at abc.com
250 2.1.0 a at abc.com... Sender ok
rcpt to:fdafdsdasdf at domain.com
550 5.7.1 fdafdsdasdf at domain.com... fdafdsdasdf at domain.com... No such user
rcpt to:valid at domain.com
250 2.1.5 valid at domain.com... Recipient ok


Bounce message header:
-------------------------
Return-Path: <g>
Received: from localhost (localhost)by mimedefang_server (8.13.8/8.13.8) id 
l0GJSJuE006458;Tue, 16 Jan 2007 11:28:19 -0800 (PST)
Date: Tue, 16 Jan 2007 11:28:19 -0800 (PST)
From: Mail Delivery Subsystem <MAILER-DAEMON>
Full-Name: Mail Delivery Subsystem
Message-Id: <200701161928.l0GJSJuE006458 at mimedefang_server>
To: <invmp at kirchenboerse.de>
MIME-Version: 1.0
Content-Type: multipart/report; 
report-type=delivery-status;boundary="l0GJSJuE006458.1168975699/mimedefang_server"
Subject: Returned mail: see transcript for details
Auto-Submitted: auto-generated (failure)

The original message was received at Tue, 16 Jan 2007 11:28:16 -0800 (PST)
from 88-109-190-72.dynamic.dsl.as9105.com [88.109.190.72]
   ----- The following addresses had permanent fatal errors -----
<invalid at dom.com>
    (reason: 550 5.1.1 <invalid at dom.com>... User unknown)
   ----- Transcript of session follows -----
... while talking to internal_server.:
>>> DATA
<<< 550 5.1.1 <invalid at dom.com>... User unknown
550 5.1.1 <invalid at dom.com>... User unknown
<<< 503 5.0.0 Need RCPT (recipient)