[Exim] autoreply for unknown users

Hi Exim-users!

I need totaly changed form of error message when local user wasn't found
by directors. So.. my last director (smartuser driver) uses autoreply
transport to send the expl. message back to sender. I've tried it with
smartuser + pipe, but it generates standard error message with pipe
stdout embeded in it.. :< Ok, everything is cool now, with autoreply and
some simple checks I'm able to simulate 'unknown user' error. I'm using
external file containing variables, which are to be expanded
($original_local_part, $original_domain, $message_headers,
$message_body...etc). But I need just one more thing I'm currently unable
to obtain - original message's Message-ID: header. I would like to
put the value into the body of my generated reply in form like:

Your message, with ID = <*****right here******> cannot be delivered to
local recipient.

I've also tried with In-Reply-To: but it seems I didn't hit the right
message so $h_in-reply-to was mistake..

Is there any elegant solution?

cheers,
Pawel

--
Pawel Wilk <siefca@???> Member of the GNU generation