[Exim] exim-4 and courier delivery

I've problems with exim-4 and courier delivery

The config file contains
the router:

courier_user:
driver = accept
require_files = "MAILBOXES/${substr_0_1::${local_part}}/${local_part}"
retry_use_local_part
transport = local_maildir

and the associated transport

local_maildir:
  driver = pipe
  check_string = ""
  command = "/usr/local/courier-imap/bin/deliverquota -w 90 \
             MAILBOXES/${substr_0_1:${local_part}}/${local_part}"
  delivery_date_add
  envelope_to_add
  user = exim
  group = mail
  log_output
  message_prefix = ""
  message_suffix = ""
  return_output
  return_path_add

but the delivery goes wrong with the following type of logfile entry

2003-03-18 12:13:44 18vF2O-0000ON-41 <= xxx@??? H=mail.zrz.tu-berlin.de [130.149.4.15] P=esmtp S=2608 id=000801c2ed3f$3550b740$0545a8c0@Patrick T="AW: " from <xxx@???> for zzz@???
2003-03-18 12:13:44 18vF2O-0000ON-41 unable to set gid=12 or uid=777 (euid=777): local delivery to zzz <zzz@???> transport=local_maildir
2003-03-18 12:13:44 18vF2O-0000ON-41 failed to read delivery status for zzz@??? from delivery subprocess
2003-03-18 12:13:44 18vF2O-0000ON-41 pipe transport process returned non-zero status 0x0100: exit code 1
2003-03-18 12:13:44 18vF2O-0000ON-41 == zzz@??? R=courier_user T=local_maildir defer (-1)
2003-03-18 12:13:44 18vF2O-0000ON-41 Frozen

Local/Makefile contains EXIM_USER=exim
/etc/passwd    contains exim:x:777:777:A...
/etc/group     contains mail:x:12:mail,postfix
                                               ^- Must I add "exim" here ?

Any pointers to solve the problem are welcome.

Regards        _______________________________________________________________
Frank Elsner  /                         c/o  Technische Universitaet Berlin   |
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