You can configure the Help Desk and activate/deactivate it from this page.
To enable/disable the Help Desk, click the respective icon - Enable or Disable.
When enabling the Help Desk, you also need to specify an arbitrary server id for identification in the Server id field, enable the Allow customers to submit tickets checkbox, and select the default queue, priority and category. Click OK. Now clients, domain administrators, and mailbox users can submit the trouble tickets to the Help Desk.