[Dovecot] statistics on proxy ???

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