[Exim] Restricting Aliases for Majordomo Lists

well, I've been pouring through the archives and I'm not having much
luck finding a simple soloution to this problem...

Here's the mail header from the last mailing of our newsletter I sent
out:

Received: from majordomo by landau.labnet.com with local (Exim 3.22 #1
(Red Hat Linux))
id 17I1Fc-0006ti-00
for <1023882439@???>; Wed, 12 Jun 2002 01:05:00 -0500
From: "Texas Cooking Newsletter" <txmailbox@???>
To: <txcooking-list@???>
Subject: Texas Cooking Newsletter, June 2002
Date: Wed, 12 Jun 2002 01:02:17 -0500
Organization: Texas Cooking Online
Message-ID: <019f01c211d6$b4a54a00$9865fea9@GORN>
Sender: owner-txcooking-list@???
Precedence: special-delivery
Reply-To: txmailbox@???
Status: O


After being the embarassed one to have a user's infection with the HaHa
virus finding the <1023882439@???> in the header and manage to
send 2 or 3 copies of the HaHa virus to the entire mailing list (14,500
e-mail addresses) I would like to restrict the outbound alias (now
renamed to txcoooking-list-outgoing & possibly moving all the outbound
aliases into their own alias files) so that only majordomo can send a
message to them. (not sure if user = would be majordom or
majordomo@localhost)

for now, I've just #'ed out the majordomo outbound alias for that list.

Thanks in advance for any help.