[Dovecot] acl, shared folders

[Infoomatic]

Hi list,
 
After spending quite some time to figure out how users can share folders I now hope someone of you could help me out. I am quite sure its just a stupid mistake/misunderstanding ... I am using Ubuntu 12.04 LTS with the shipped dovecot 2.0.19
When I login via telnet as user1 I get the following:
1 create folder1
1 OK Create completed.
2 setacl folder1 user2 rli
2 OK Setacl complete.
3 getacl folder1
* ACL "folder1" "user2" ilr "user1" lrwstipekxacd
3 OK Getacl completed.
 
This seems fine. However, there is nothing listed in the account of user2. I think the mistake is in the namespace configuration of "location" or "prefix"
 
Please help! Thanks!
 
infoomatic
 
# 2.0.19: /etc/dovecot/dovecot.conf
# OS: Linux 3.2.0-45-generic x86_64 Ubuntu 12.04.3 LTS ext4
auth_username_format = %n
disable_plaintext_auth = no
mail_debug = yes
mail_gid = vmail
mail_home = /var/lib/vmail/home/%u
mail_location = mdbox:/var/lib/vmail/mail/%u
mail_plugins = " acl zlib fts fts_solr acl"
mail_uid = vmail
managesieve_notify_capability = mailto
managesieve_sieve_capability = fileinto reject envelope encoded-character vacation subaddress comparator-i;ascii-numeric relational regex imap4flags copy include variables body enotify environment mailbox date ihave imapflags
mdbox_rotate_size = 64 M
namespace {
  inbox = yes
  location =
  prefix =
  separator = /
  type = private
}
namespace {
  list = children
  location = mdbox:/var/lib/vmail/mail/%%n/mailboxes/shared/%n
  prefix = shared/%%n/
  separator = /
  subscriptions = no
  type = shared
}
passdb {
  args = /etc/dovecot/dovecot-ldap.conf.ext
  driver = ldap
}
plugin {
  acl = vfile
  acl_shared_dict = file:/var/lib/vmail/shared-mailboxes
  fts = solr
  fts_solr = break-imap-search url=http://localhost:8080/solr/
  sieve = ~/.dovecot.sieve
  sieve_dir = ~/sieve
  sieve_extensions = +imapflags
  zlib_save = bz2
  zlib_save_level = 6
}
protocols = " imap sieve pop3"
service auth {
  unix_listener /var/spool/postfix/private/auth {
    group = postfix
    mode = 0660
    user = postfix
  }
  unix_listener auth-userdb {
    group = vmail
    user = vmail
  }
}
service managesieve-login {
  inet_listener sieve_deprecated {
    port = 2000
  }
}
ssl_cert = </etc/ssl/certs/dovecot.pem
ssl_key = </etc/ssl/private/dovecot.pem
userdb {
  args = /etc/dovecot/dovecot-ldap.conf.ext
  driver = ldap
}
protocol lda {
  mail_plugins = " sieve acl"
}
protocol imap {
  mail_plugins = " acl imap_acl"
}