Plugin de cuotas y avisos

Actívalo en 90-quota.conf:

plugin {
  quota = maildir:User quota
  quota_status_success = DUNNO
  quota_status_nouser = DUNNO
  quota_status_overquota = "552 5.2.2 Mailbox is full"
}

protocol lmtp {
  postmaster_address = postmaster@example.com
  mail_plugins = $mail_plugins quota sieve
}

protocol imap {
  mail_plugins = $mail_plugins imap_quota
}

Cuota por usuario desde el quota_rule de userdb (por ejemplo, *:bytes=5G).

Correos de aviso al 80% / 95% mediante el servicio quota-warning:

plugin {
  quota_warning  = storage=80%% quota-warning 80 %u
  quota_warning2 = storage=95%% quota-warning 95 %u
}
service quota-warning {
  executable = script /usr/local/bin/quota-warning.sh
  unix_listener quota-warning {
    user = vmail
  }
}

quota-warning.sh ejecuta mail para enviarle un aviso al usuario.