[Dovecot] Dovequota Mbox - NFS - Quota Does not work

[Il Neofita]

Hi
I am not able to get the quota out from dovecot
I have tried with thunderbird and roundcube without luck
this is my conf

# 2.0.beta6 (3156315704ef): /etc/dovecot/dovecot.conf
# OS: Linux 2.6.32-71.14.1.el6.x86_64 x86_64 Red Hat Enterprise Linux
Server release 6.0 (Santiago)
mail_debug = yes
mail_location = mbox:~/mail:INBOX=/mail/spool/%u:INDEX=/mail/indexes/%u
mbox_write_locks = fcntl
passdb {
  driver = pam
}
plugin {
  mail_log_events = delete undelete expunge copy mailbox_delete mailbox_rename
  mail_log_fields = uid box msgid size
  quota = fs:INBOX:mount=/mail
  quota2 = fs:ROOT:mount=/home
}
ssl_cert = </etc/pki/dovecot/certs/dovecot.pem
ssl_key = </etc/pki/dovecot/private/dovecot.pem
userdb {
  driver = passwd
}
protocol imap {
  imap_logout_format = bytes=%i/%o
  mail_max_userip_connections = 10
  mail_plugins = imap_quota quota
}

What I am doing wrong?