[Mailman-Users] sender bounce line?

[dave]

We have a list that appears to be filtered by recipients at verizon. 
Specifically, they can post but never receive and are ultimately 
unsubscribed due to bounces.  mailman logs look otherwise normal.
The theory is that the line:

Sender:[EMAIL PROTECTED]
triggers filtering by verizon which sounds bogus to me. More likely, it's
the users MUA as defined in
  http://www.washington.edu/computing/mailman/faqs/mailman.header.html
Haven't had a chance yet to talk to one of these people and get more
details and try to talk directly to port 25 and add that line. If
that is the case, I'm tempted to modify the bounces alias for that 
list altho that seems a harsh way to fix things.

Has anyone else had a similar problem? Is the above header configurable?
Can it be turned off somehow?
Thanks

 =-=-=-=-=-=-=-=-=-=-  generated by /dev/dave -=-=-=-=-=-=-=-=-=-=-=-=
 David Stern                                    University of Maryland
           Institute for Advanced Computer Studies
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