How to empty a queue with 200+ messages?

PubSub+ Event Broker
6

Hi Richard,
I have tried it from Postman using a POST {{url}}/SEMP and the following payload:

<rpc>
  <admin>
    <message-spool>
      <vpn-name>my VPN</vpn-name>
      <delete-messages>
        <queue-name>my queue</queue-name>
      </delete-messages>
    </message-spool>
  </admin>
</rpc>

I get an HTTP 200 OK response, but nothing happens. If I send an invalid XML payload (removing a tag), I still get an HTTP 200. The documentation says:

_An HTTP response of “200 OK” is returned if the command was accepted by the event broker (even if it was not successfully executed).
_

How does the SEMP V1 operation work?