tunable rejection message for non-members?

[David-abrahams]

I got this at the end of a bitter complaint from someone
who couldn't
figure out how to get into our mailing lists starting from
GMane:

> I also recommend cleaning up the newsgroup
registration procedure so
> that people who are not aware of the unusual
requirement of
> pre-registration are told why it exists and how to deal
with it.
> For example, I got this back when I first tried to post:
>
> You are not allowed to post to this mailing list, and
your message has
> been automatically rejected. If you think that your
messages are
> being rejected in error, contact the mailing list owner
at
> <email address hidden>.

It appears Mailman allows us to tune the message
that "moderated
members" get when they post. Ours is:

  You are posting to a moderated mailing list from an
email address
  that is not subscribed to the list.

  To facilitate the moderators job, we insist that all
postings come
  from email addresses that are subscribed to the list
(this does not
  mean that you have to receive individual emails from
the list, or
  that you can't use a news group alias to access and
post to the
  list, just that you must register first).

  Please visit
http://lists.boost.org/mailman/listinfo.cgi/boost to
  register with the list.

  Thankyou,

  The Boost List Moderators

Unfortunately, it doesn't seem to have a way to tune
the message given
to users who aren't members. If we want to keep
spammers out by
requiring registration before posting, *and* we want to
moderate
first-time posts, but we want users to get a nice
explanation of how
to get posting privileges, what can we do?

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