Threading is foobared?

[Random832]

On Thu, Mar 31, 2016, at 01:25, Random832 wrote:
> > if a message is cross-posted to two lists which both gateway to Usenet,
> > and Mailman didn't make the Message-IDs unique, the news server would
> > discard one of the two posts as a duplicate and the post would be
> > missing from one of the recipient Usenet groups.

One additional thing that would be nice and would solve most of the
duplicate problem with hypothetically including the rewritten
Message-IDs in outgoing emails, would be to detect crossposts to
multiple lists in the same Mailman instance, and to send them to Usenet
(and to subscribers) as a single message, with appropriate headers for a
crosspost.