[Mailman-Users] List subscribers receiving duplicate messages: help!

[Iain D.Brown]

Dear fellow Mailman users,

I have just started using Mailman for a large Society mailing list
(~500 subscribers), and have run into two problems that are
causing a lot of heat on my new list.

  Problem 1: when a subscriber replies to a message that is part
  of a lengthy thread, their email client is listing the addresses
  of all previous respondents to the thread, eg: A thread on
  Mickey Mouse on the list disney.example.dom has attracted
  postings from minnie at disneyexample.com, mickey at disneyexample.com
  and pluto at plutoexample.com. When I come to reply to a message,
  my email client is putting the following in the To and CC
  fields:

    To: pluto at plutoexample.com
    CC: minnie at disneyexample.com, mickey at disneyexample.com,
    list at disney.example.dom
    From: iain at iainbrown.net
    Message: Rhubarb, rhubarb, rhubarb.

  I know munging the Reply-To, to force all responses to be sent
  to list at disney.example.dom, is not the done thing. So is there
  any way of making Mailman clean up the header information,
  perhaps to remove all the names in the CC field except for the
  list address?

Problem 2: (which is related to problem 1) when a subscriber
  replies to a message, Mailman does not take notice of the
  addresses in the To: or CC: fields, and thus some subscribers
  are receiving multiple copies of messages, even though their
  settings say "No Dupes". To continue the example from above,
  poor Minnie, Pluto and Mickey are all receiving duplicates of
  the message from me -- once via the list and once from me
  direct. What would be causing this?

I am using Mailman 2.1.2 offered by my Web host; they can't
upgrade to 2.1.5 because they have a number of custom
modifications which means an upgrade is not trivial. And they are
not prepared to run a single Mailman instance for every customer
as would not be feasible.

Any suggestions and advice on how to sort out my problems?

Many thanks.

Best wishes,

Iain.

-- 
Iain Brown
iain at iainbrown.net