Illegal request format when accepting or rejecting

Hi,

I've got a moderated mailing list.  I read the mailbox from the moderator
with Mozilla Thunderbird.

I receive the message asking me to accept or reject.  I reply to this
message or I click the link included or I send a new mail to the specified
address (it makes no difference if I use the accept or the reject-address).
Either way, I get the following error from ezmlm:

ezmlm-moderate: fatal: Illegal request format (#5.7.1)

Sending accept- or reject-mails through a web-based interface or through
Outlook seems to work.  Any clues what is wrong here ?

I'm using:
* ezmlm 0.53
* ezmlm-idx 5.1.0

Kind regards,

Ketje

PS: Here you find some headers of the mail I'm trying to send to my ezmlm
(which invokes the error):

Return-Path: <[email protected]> <[email protected]>
Received: (qmail 2624 invoked by uid 0); 21 Nov 2006 11:27:06 -0000
Received: from ipaddress by ns (envelope-from <[email protected]>
<[email protected]>, uid 92) with qmail-scanner-1.24st
 (f-prot: 4.6.6/3.16.14. perlscan: 1.24st.
 Clear:RC:0(ipaddress):.
 Processed in 0.246198 secs); 21 Nov 2006 11:27:06 -0000
X-Qmail-Scanner-Mail-From: [email protected] via servername
X-Qmail-Scanner: 1.24st (Clear:RC:0(192.170.200.2):. Processed in
0.246198 secs Process 25756)
From: me <[email protected]> <[email protected]>
To: [email protected]
<testje1-accept-1164108350.25127.ngomhabgcnhgedgohpbf@mailing.ehb.be>
Message-ID: <[email protected]> <[email protected]>
Date: Tue, 21 Nov 2006 12:27:58 +0100
User-Agent: Thunderbird 1.5.0.8 (Windows/20061025)
MIME-Version: 1.0
Subject: ok
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit

ok