[Dovecot] statistics on proxy ???

[Marco Giunta]

Hi at all,
could I have imap statistics on my dovecot proxy server ??
Here my config:

# 2.1.13: /etc/dovecot/dovecot.conf
...
mail_plugins = stats
...
plugin {
  ...
  stats_refresh = 30 secs
  stats_track_cmds = yes
}
...
service stats {
  fifo_listener stats-mail {
    mode = 0666
  }
}
...
protocol imap {
  ...
  mail_plugins = stats imap_stats
}


File '/var/run/dovecot/stats' is always 0 byte:

# ls -la /var/run/dovecot/stats
srw-------. 1 root root 0 Feb 18 14:24 /var/run/dovecot/stats

and 'dovecotadm' say always:

# doveadm stats dump session
doveadm(root): Info: no statistics available


Is there something wrong in my config, or stats are not available on 
proxy ???

Cheers,
  Marco