[Dovecot] no local users - mbox all under /var/spool/mail/

[Daniel]

Hi there,
im new to dovecot but I made my way trough configuring it. I almost get 
it running at least for one IMAP user. The problem is I got no local 
user thus no home directories, all Mailboxes are in mbox format under: 
/var/spool/mail:
Looks like this:

-SNIP-
drwx------    3 web1p2   poponly        19 2004-08-13 00:05 indexes
-rw-------    1 nobody   nobody          0 2004-03-26 21:51 nobody
-rw-------    1 root     root            0 2004-03-26 21:51 root
-rw-------    1 web1p2   poponly        14 2004-08-13 00:10 .subscriptions
-rw-------    1 web1p2   poponly      8571 2004-08-13 00:10 Trash
-rw-rw----    1 web0p1   root     23068262 2004-08-12 21:27 web0p1
-rw-rw----    1 web0p2   root        17749 2004-08-12 23:55 web0p2
...
-SNAP

I´ve set up the mail-environment this way:
default_mail_env = 
mbox:/var/spool/mail/:INBOX=/var/spool/mail/%u:INDEX=/var/spool/mail/indexes/%u

The problem is, that the directory "indexes" has permisions that only 
the owner can write to (well, I could change permissions, but?) and that 
the ".subscription" file and "Trash" folder is directly in this 
directory. So if I add a second user (e.g. web0p1) I got error messages 
imho due to the use of the "same" folder....?

What would be the proposed setup for this system with mostly non-local 
users without real home directories and all their mbox in a shared 
directory?


Thanks for your time!

Daniel