[Dovecot] 2.0.12 (fa2e92526716): Deleting mails and folders from public namespaces

[Binarus]

Hello,

we basically run a dovecot imap setup where users' mailboxes are in
private namespaces (as usual), but there is a public namespace with
several thousand deeply nested folders also.

The client we use is Thunderbird 3. The public namespace shows up in
each user's account at the top level (i.e. same level as Inbox, Sent and
so on), and users can make new subfolders in the public namespace, copy
mails to it and so on. So, our setup basically works.

But whenever a user tries to delete a folder from the public namespace,
dovecot gives the following error: "Renaming not supported across
non-private namespaces".

I think I have a grasp why this happens (Thunderbird tries to move the
folder from the public namespace into the trash folder (private
namespace) of the user who does the deletion), and I also have read
Timo's statement that he does not plan to support such renaming due to
big problems he is seeing with it.

Nevertheless, since deleting a folder from a public archive is not a too
uncommon thing, I wanted to ask how other people have solved that.

It came to my mind to configure Thunderbird to immediately delete
folders and messages (instead of moving them to trash folder). I have
tested that, and it worked, but is somehow dangerous and unsatisfying.

Furthermore, I haven't completely understood the reason for the
different behaviour of folders in the public namespace and a single
message therein.

If I configure Thunderbird to use the trash folder, users can delete
messages from the public namespace, i.e. Thunderbird can move messages
from the public namespace to the private trash folder of the respective
account.

This is obviously not true for folders (even if they are empty). What's
the difference between an empty folder and a single message in this
respect? Is it really the ACL thing which makes folders so difficult to
handle opposed to single messages?

Thank you very much for any ideas!

Regards,

Peter

************
dovecot -n:

# 2.0.12 (fa2e92526716): /etc/dovecot/dovecot.conf
# OS: Linux 2.6.32-5-amd64 x86_64 Debian 6.0.1
auth_verbose = yes
auth_verbose_passwords = sha1
first_valid_uid = 103
maildir_copy_with_hardlinks = no
namespace {
  hidden = no
  inbox = yes
  list = yes
  location =
maildir:/home/vmail/content/users/%u:INDEX=/home/vmail/index/users/%u
  prefix =
  separator = /
  subscriptions = yes
  type = private
}
namespace {
  hidden = no
  inbox = no
  list = yes
  location =
maildir:/home/vmail/content/archive:INDEX=/home/vmail/index/archive
  prefix = Archive/
  separator = /
  subscriptions = yes
  type = public
}
passdb {
  args = scheme=SSHA username_format=%u /etc/dovecot/users
  driver = passwd-file
}
plugin {
  acl = vfile
}
protocols = " imap"
service auth {
  user = root
}
service imap-login {
  inet_listener imap {
    port = 0
  }
  inet_listener imaps {
    address = 192.168.20.140
    port = 993
    ssl = yes
  }
}
ssl_cert = </etc/dovecot/imap-ssl.home.omeganet.de.crt
ssl_key = </etc/dovecot/imap-ssl.home.omeganet.de.key
userdb {
  args = uid=vmail gid=vmail home=/home/vmail/content/users/%u
  driver = static
}
protocol imap {
  mail_plugins = acl imap_acl
}