[Dovecot] quota doesn't work?

[Mauro Sanna]

I'm using dovecot 1.0.rc15 with debian etch.
        In dovecot.conf I have set  
        mail_plugins = quota imap_quota for imap
        mail_plugins = quota for pop3
        and quota = maildir:storage=10240.
        I seems that it doesn't work 'cause I send messages over 10M and
        it
        doesn't block my maildir box.
        I have to do something more?