You can take advantage of our SpamExperts email filtering even if you're using third party DNS/nameservers. To make sure your domains email is passed through our SpamExperts filtering servers when using third party nameservers you should set your MX records to:
mx1.arandomserver.com Priority 0
mx2.arandomserver.com Priority 10
mx3.arandomserver.com Priority 20
mx4.arandomserver.com Priority 30