[Mailman-Users] Problem enforcing text/plain posts only policy

[Tim Hutchinson]

Hi,

I have recently begun enforcing a plain text only policy based on the 
instructions in FAQ 3.10: 
http://www.python.org/cgi-bin/faqw-mm.py?req=all#3.10
(adding header values to Privacy Options -> Spam-specific posting 
filters, e.g. Content-Type: .*mixed)

The problem is that this has cast the net a little too wide.  At least 
one subscriber use AVG virus protection software, which adds a text 
attachment to every e-mail.  This results in a header of 
multipart/mixed, so the post gets held as having a suspicious header.  

More specifically, an example of a complete Content-type line is
Content-type: multipart/mixed; 
boundary="Boundary_(ID_Pcxr7Y3chQ46Gj8lLo/M5A)"; x-avg-checked=avg-ok

Is there anyway to match against "x-avg-checked", say, so that posts 
will be held if they include .*mixed, but not x-avg-checked.  I tried
Content-Type: .*mixed(?!x-avg-checked)
but this doesn't seem to work.  (I couldn't find any details about the 
regex syntax that mailman supports.)
 
Thanks
Tim