The Mailman gateway seems to be picking posts
up from the newsgroup and then reposting them
to the newsgroup. As an example, see my post in
the interminable PrePEP: Decimal Data Type
thread dated 11/6/2003 at 3:49 PM.
It showed up again from the mailing list to newsgroup
gateway just after 12:30 on 11/7, but still dated 11/6,
and formatted text/plain.
There are a number of other posts in this, and I think
other, threads that have also been double posted
this way.
John Roth