Spam getting through to list

I have several lists configured the same way, with ezmlm-make -Mu

I know that spam with sender faked to a list member will get through. But
that is not my problem.

For one list only, spam is getting through even though the sender (real or
faked) is not a list member. I don't understand how this is happening or
what to do about it.

 * Is there a misconfiguration by me?

 * Is this unavoidable?

 * Have spammers found a new way to get through ezmlm?

I've temporarily changed the list to moderated -mU and hence can see the
headers of the incoming spam. Here's a sample:

Return-Path: <[email protected]>
Delivered-To: moderator for [email protected]
Received: (qmail 90709 invoked from network); 16 Feb 2008 16:08:06 -0000
Received: from ip154-79-208-87.adsl2.versatel.nl (87.208.79.154)
  by myserver.myhost.com with SMTP; 16 Feb 2008 16:08:06 -0000
Received: from tfeon ([42.46.164.93]) by ip154-79-208-87.adsl2.versatel.nl
with Microsoft SMTPSVC(6.0.3790.0); Sat, 16 Feb 2008 16:53:38 +0100
Message-ID: <002c01c870b4$1891ed60$5da42e2a@tfeon>
From: <[email protected]>
To: <[email protected]>
Subject: (subject edited so it doesn't trigger your spam trap).
Date: Sat, 16 Feb 2008 16:53:38 +0100
MIME-Version: 1.0
Content-Type: text/plain;
	format=flowed;
	charset="windows-1252";
	reply-type=original
Content-Transfer-Encoding: 7bit
X-Priority: 3
X-MSMail-Priority: Normal
X-Mailer: Microsoft Outlook Express 5.50.4131.1600
X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4131.1600


[email protected] is not a subscriber to mylist, nor on the allow list, so
how come (when I had it set to -Mu) messages like this were passed to the
list?

Is there some configuration change I can make to overcome this, or do I (and
all of you) have to resign myself to having to make all my lists moderated
:(

Thanks


-- 
Simon Child