shared mailboxes and ACLs? Lion Server

Hello!

I´ve managed to setup shared mailboxes with dovecot in Lion Server (not public mailboxes).
Now I have to setup the ACLs manually for every user!

Now I am fighting with “ACL groups” and found something about “post-login scripts” and I wrote a post-login script “dovecot_postlogin.sh” containing this:
#!/bin/sh
ACL_GROUPS=`groups $USER | tr ' '  ','`
export ACL_GROUPS
export USERDB_KEYS="$USERDB_KEYS acl_groups"
exec "$@“

No I tried to find out how to setup the dovecot-config ti use this script - but had no success :-(
I wonder where to tell dovecot to use this script.

Here is what I have done to activate “shared mailboxes”:
activate acl plugin in 10-mail.conf
setup namespace in 10-mail.conf
setup acl as vfile  in 90-mail.conf

And setup the shared mailboxes in /var/spool/imap/dovecot/mail/“sharedmailboxname” and the needed dovecot-acl files.

I just can not find out how to make ACL groups working.

Every hint is welcome, bye
eweri

P.S. Looked at
http://wiki2.dovecot.org/PostLoginScripting
http://wiki2.dovecot.org/SharedMailboxes/Shared
http://wiki2.dovecot.org/ACL