[Dovecot] Imap service and quota

[Miguel]

Hi, i have just migrated from courier-imap to dovecot. im using it with 
vpopmail, the pop service is working ok but the imap service for imp 
webmail is not writing the quota information to the maildirsize file, as 
recommended in the docs, i have this in dovecot.conf :

plugin {
   # Quota plugin. Multiple backends are supported:
  #   dirsize: Find and sum all the files found from mail directory.
  #            Extremely SLOW with Maildir. It'll eat your CPU and disk I/O.
  #   dict: Keep quota stored in dictionary (eg. SQL)
  #   maildir: Maildir++ quota
  #   fs: Read-only support for filesystem quota
  quota = maildir

  }

This only happend with imp/imap, there is not problem using a pop client
Regards,