The email I just wrote came with the correct set of headers.

On Mon, 2012-09-17 at 22:13 +0200, Stefan G. Weichinger wrote:
> Am 17.09.2012 22:09, schrieb Michael Tremer:
> > I had a look at an older email, which had these headers...
> > 
> > Restarted mailman and disabled -> enabled the RFC 2369 option.
> > 
> > Let's see...
> 
> I don't see it :-)
> 
> As mentioned: I can filter for other header-info.
> 
> AFAI know mailman is capable to provide that info, as I use it for many
> other lists.
> 
> Stefan
>