I've got inn-2.4.2-1.
"xhdr newsgroups" lies -- it doesn't return the actual Newsgroups
header of the article, but rather a list of newsgroups with all groups
that aren't available on the server stripped out.
This behavior is patently incorrect. Just because a particular
newsgroup doesn't exist on my server doesn't mean it shouldn't be
preserved in the Newsgroups line when I follow up on a posting. With
the behavior I described above, if my News reader uses xhdr to
determine the list of newsgroups to which the post a followup, which
it does in fact do and which is a perfectly reasonable thing to do,
it'll get it wrong.
As far as I'm concerned this is a violation of the NNTP spec. The
xhdr command is supposed to return the actual message header, not the
header as INN chooses to pervert it.
It sounds like INN is trying to optimize the response by looking in the x-ref in
the overview rather than having to re-parse the article, because that's the
behaviour of x-ref. You're right, that's a violation of RFC-2980.
Will be fixed in version 2.4.3...