[Dovecot] Help with Public Folder Configuration

[Joy]

Dear All,
               I am trying to use Public Folder feature of dovecot but
having some confusion with the configuration part as well as
understanding the same.

Here is output of doveconf -n which i think required to help me -

mail_location = maildir:~/Maildir

namespace {
  inbox = yes
  location =
  prefix =
  separator = .
  type = private
}
namespace {
  list = children
  location = maildir:/var/mail/public
  prefix = Public.
  separator = .
  subscriptions = no
  type = public
}

plugin {
  acl = vfile:/usr/local/dovecot/dovecot-acl/acl
}

 after making this configuration i also created subfolder inside
/var/mail/public

which looks like following:-

mail1:~# less /var/mail/public/
dovecot-acl-list  .Public/
mail1:~# less /var/mail/public/.Public/Maildir/
cur/     new/         tmp/


I have changed default permission to [ chown -R vmail:vmail /var/mail
] on base public folder.

Now I am able to see the public folder from webmail as well as from
thunderbird but no display for .Public folder.

I am expecting that .Public folder will be visible to all but no one
will be allowed to delete and make any change in that folder, I am
also using global ACL in my configuration.

Please let me know what i am doing wrong because not getting any error
in log, Correct me if i am understanding wrong.

Thanks