[Dovecot] quota: maildrop + dovecot. dovecot doesn't update maildirsize file

[Frittella Laurento]

Hi all,
I'm trying to implement quota support in postfix using maildrop +
dovecot but I think dovecot doesn't update info stored in maildirsize file.

# 1.0.2: /etc/dovecot/dovecot.conf
base_dir: /var/run/dovecot/
listen: 127.0.0.1
ssl_listen: *
ssl_ca_file: ...
ssl_cert_file: ...
ssl_key_file: ...
ssl_cipher_list: ALL:!LOW:!SSLv2
login_dir: /var/run/dovecot/login
login_executable: /usr/libexec/dovecot/imap-login
valid_chroot_dirs: /home/vmail/domains
first_valid_uid: 1001
last_valid_uid: 1001
first_valid_gid: 1001
last_valid_gid: 1001
mail_location: maildir:/home/vmail/domains/%d/%n
auth default:
  user: dovecot-auth
  passdb:
    driver: ldap
    args: /etc/dovecot/dovecot-ldap.conf
  userdb:
    driver: ldap
    args: /etc/dovecot/dovecot-ldap.conf
plugin:
  quota: maildir:ignore=Trash

When a mail arrives maildrop delivers it and update info in the
maildirsize file, but when I delete messages through dovecot (using
thunderbird) the maildirsize remains the same and so users reach
overquota very soon.

What's wrong?

Thanks in advance,
Laurento