This function sets Exim's queue to suspend and force failure for email that a user sends to an external address.

Note:

If mail for a cPanel user's account is suspended, the system will reject their email before the mail server puts it in queue.

{
  "metadata": {
    "command": "suspend_outgoing_email",
    "reason": "OK",
    "result": 1,
    "version": 1
  }
}