[exim] mailman: Group mismatch error

Good afternoon

I have the following setup:

Debian 5.0.8
exim4                         4.69-9+lenny4
mailman                       1:2.1.11-11+lenny2

I read the documentation that comes with mailman, including
/usr/share/doc/mailman/README.Exim4.Debian and I made the proposed
changes to my exim configuration and to mm_cfg.py, then restarted
mailman and exim. Still I receive the following error, when I want to
send an e-mail to the newly created list:

Group mismatch error. Mailman expected the mail
wrapper script to be executed as group "daemon", but
the system's mail server executed the mail script as
group "Debian-exim". Try tweaking the mail server to run the
script as group "daemon", or re-run configure,
providing the command line option `--with-mail-gid=Debian-exim'.


And again: Any suggestions welcome!

Thanks
Stef