[Mailman-Users] want gid 500 not 100

[mailinglists at belfin.ch]

Hello

This is the error I get upon confirming my subscription:

This is the MS Exchange 2003 XP Bugfree program at host lists.seaan.net.

I'm sorry to have to inform you that the message returned
below could not be delivered to one or more destinations.

For further assistance, please send mail to <postmaster>

If you do so, please include this problem report. You can
delete your own text from the message returned below.

			The MS Exchange 2003 XP Bugfree program

<mailman-request at lists.seaan.net>: Command died with status 2:
    "/usr/local/mailman/mail/mailman request mailman". Command output:
Failure
    to exec script. WANTED gid 500, GOT gid 100.  (Reconfigure to take 100?)


checking the /usr/local/mailman/mail/mailman it is group mailman user
mailman both gid 500 and uid 500. 
to be precise hte directory looks like this:

-rwxr-sr-x    1 mailman  mailman     38452 Oct  7 15:06 mailman


What am I doing wrong?

Thanks,
philipp

ah, yes, mailer is postfix