[Mailman-Users] Clear the "Importance:" flag (or how to clear certain headers)?

[Ralf Hildebrandt]

One of my lists' members is complaining about the "Importance:" flag
not being cleared for mails passing through the list:

From: "sender, Heike" <Heike.Sender at charite.de>
To: "'fleamarket at charite.de'" <fleamarket at charite.de>
Importance: high
X-Priority: 1
Date: Tue, 15 Mar 2011 10:39:33 +0100
Thread-Topic: Suche Videorekorder
Thread-Index: Acvi9OP5K98V+31vSQuzl4GsbSPJSA==
Message-ID: <6FDCB96F850BF34591250B4EDBBA5F79012D2F6F15 at EXCHANGE41.charite.de>

So, how can I clear that header line from mails passing through that
particualr list?

-- 
Ralf Hildebrandt
  Geschäftsbereich IT | Abteilung Netzwerk
  Charité - Universitätsmedizin Berlin
  Campus Benjamin Franklin
  Hindenburgdamm 30 | D-12203 Berlin
  Tel. +49 30 450 570 155 | Fax: +49 30 450 570 962
  ralf.hildebrandt at charite.de | http://www.charite.de