[kmike]

My point is, there're too many MTAs sending out non-RFC compliant DSN's out there. For some insight, look at the Mail:eliveryStatus::BounceParser perl module source. I guess eventually you'll write something similar using PHP
Here's qmail bounce I was speaking of:

From MAILER-DAEMON  Wed Jun 22 08:27:25 2005
Return-Path: <MAILER-DAEMON>
Received: from mxavas2.aruba.it (mx3.aruba.it [62.149.128.132] (may be forged))
        by xxxxxxxxxxxx with SMTP id j5MDR182012646
        for xxxxxxxxxxxxxxx; Wed, 22 Jun 2005 08:27:07 -0500
Message-Id: xxxxxxxxxxxx
Received: (qmail 2289 invoked for bounce); 22 Jun 2005 13:26:56 -0000
Date: 22 Jun 2005 13:26:56 -0000
From: MAILER-DAEMON@mxavas2.aruba.it
To: xxxxxxxxxx
Subject: failure notice

Hi. This is the qmail-send program at mxavas2.aruba.it.
I'm afraid I wasn't able to deliver your message to the following addresses.
This is a permanent error; I've given up. Sorry it didn't work out.

<lmasali@demo.eu.blackberry.net>:
193.109.81.50 does not like recipient.
Remote host said: 550 5.2.1 <lmasali@demo.eu.blackberry.net>... Mailbox disabled
 for this recipient
Giving up on 193.109.81.50.

--- Below this line is a copy of the message.

Return-Path: xxxxxxxxxxx
.....................

Here's one from MS exchange:

From MAILER-DAEMON  Wed Jun 22 13:23:23 2005
Return-Path: <MAILER-DAEMON>
Received: ...........
Received: from huey.opc.bbhc ([10.2.18.30])
 by txuspipas004.unitedsurgical.com (SMSSMTP 4.1.4.30) with SMTP id M20050622131
85703364
 for xxxxxxxxxx; Wed, 22 Jun 2005 13:18:58 -0500
Received: by huey.unitedsurgical.com with Internet Mail Service (5.5.2653.19)
        id <M04CR85P>; Wed, 22 Jun 2005 13:19:15 -0500
Message-ID: <514220978E9FD211B11000805F0D0A79217BF258@huey.unitedsurgical.com>
From: System Administrator <postmaster@ortholink.net>
To: xxxxxxxxxx
Subject: Undeliverable: Reply to post 'Mountain Models Sportana Biplane'
Date: Wed, 22 Jun 2005 13:19:14 -0500
MIME-Version: 1.0
X-Mailer: Internet Mail Service (5.5.2653.19)
X-MS-Embedded-Report: 
Content-Type: Text/Plain

Your message

  To:      stahlmangc@ortholink.net
  Subject: Reply to post 'Mountain Models Sportana Biplane'
  Sent:    Wed, 22 Jun 2005 13:12:17 -0500

did not reach the following recipient(s):

stahlmangc@ortholink.net on Wed, 22 Jun 2005 13:19:10 -0500
    The recipient name is not recognized
        The MTS-ID of the original message is: c=us;a=
;p=ortholink;l=HUEY0506221819M04CR853
    MSEXCH:IMS:Ortholink:Information Technologies:HUEY 0 (000C05A6) Unknown
Recipient

Also, some MTAs send X-Failed-Recipients header instead of standard one.