[Dovecot] 2 users database on same LDAP with different mail location

[Francesco]

Hello,
i know i know, i'm getting annoying but appearently i always come up
with weird ideas and i cant seem to accomplish such a task.

the scenario is that i have an LDAP server with a bunch of users.
some of them are in a specific OU, and i'd like to define for all these
users belonging to this OU an alternative mail location/storage.

in details for all the users i'd like to use maildir storage in a
directory, while for the users belonging to a specific OU i'd like to
use dbox with an alternative storage attached.

so i created 2 userdb like this:

userdb {
  driver = ldap
  args = /etc/dovecot/dovecot-ldap-maildir.conf.ext
}

userdb {
  driver = ldap
  args = /etc/dovecot/dovecot-ldap-dbox.conf.ext
}

and then defined these 2 args files:
maildir:

hosts = localhost
dn = CN=ldapadmin,OU=administrators,DC=plutone,DC=local
dnpass = <password>
auth_bind = yes
ldap_version = 3
base = DC=plutone,DC=local
user_attrs = sAMAccountName=home=/var/vmail/%$

dbox:

hosts = localhost
dn = CN=ldapadmin,OU=administrators,DC=plutone,DC=local
dnpass = <password>
auth_bind = yes
ldap_version = 3
base = OU=dboxusers,OU=lowpriority,DC=plutone,DC=local
user_attrs = sAMAccountName=home=/var/local_dbox/%$,
=mail=dbox:/var/local_dbox/%$:ALT=/var/iscsi_dbox/%$
user_filter = (&(ObjectClass=person)(mail=%u))


yet it doesn't matter how hard i try if i send an email to a user
belonging to the dboxusers OU i still have the user to be addressed to
the maildir storage in /var/vmail

am i missing something?

Thanks
Francesco