trouble with "mail is looping" spam

Hi,

This is on a server with

  netqmail-1.06
  qmailadmin-1.2.15
  vpopmail - 5.4.30

Recently I began noticing many bounce-backs triggered from spam to  
non-existent addresses on domains with "catch-all" set to deleted, and  
in the message it says "mail is looping".  Example pasted below.

I'm unable to recreate this by sending to these addresses myself,  
maybe it's the way the "To" addresses are formatted by the spammers?

They don't seem to be abusing the bounce-back (yet) but they're coming  
in pretty often, more than once a minute, and it's generating a lot of  
junk.  Haven't yet been able to figure out why it's happening or how  
to stop it from bouncing.
Would greatly appreciate suggestions, thank you.


::::::::::::::
/var/qmail/queue/mess/7/786699
::::::::::::::
Received: (qmail 4726 invoked for bounce); 31 Oct 2012 14:49:21 -0000
Date: 31 Oct 2012 14:49:21 -0000
From: MAILER-DAEMON@[***REDACTED***].com
To: [email protected]
Subject: failure notice

Hi. This is the qmail-send program at [***REDACTED***].com.
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.

<erin@[***REDACTED***].com>:
mail is looping

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

Return-Path: <[email protected]>
Received: (qmail 4722 invoked by uid 89); 31 Oct 2012 14:49:21 -0000
Received: from unknown (HELO norgazdata.com) (176.223.172.3)
   by [***REDACTED***].com with SMTP; 31 Oct 2012 14:49:21 -0000
Delivered-To: erin@[***REDACTED***].com
Received: by 10.223.118.17 with SMTP id t17cs125410faq;
         Wed, 31 Oct 2012 07:49:25 -0700
Received: by 10.216.220.142 with SMTP id o14mr2820421wep.61.1316443187605;
         Wed, 31 Oct 2012 07:49:25 -0700
Return-Path: <[email protected]>
From: "ChristianMingle.com Dating Offer"  
<[email protected]>
Content-Type: multipart/alternative; boundary=Apple-Mail-3-110609711
Subject: Connect with local Christian Singles in our online community
Date: Wed, 31 Oct 2012 07:49:25 -0700
Message-Id: <[email protected]>
To:   <erin@[***REDACTED***].com>
Mime-Version: 1.0 (Apple Message framework v1084)
X-Mailer: Apple Mail (2.1084)
X-AntiAbuse: This header was added to track abuse, please include it  
with any abuse report
X-AntiAbuse: Primary Hostname - nylizzzards.info
X-AntiAbuse: Original Domain - yahoo.com
X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12]
X-AntiAbuse: Sender Address Domain - nylizzzards.info



!DSPAM:5096775f33998109284624!

--Apple-Mail-3-110609711
Content-Transfer-Encoding: 7bit
Content-Type: text/plain;
         charset=us-ascii

Most recently, it has become common for online dating websites to  
provide webcam chats between members. In
[snip]

EOM



!DSPAM:5096775f33998109284624!