Yes, this is possible. If you point your hostnames to the IP addresses of our SpamExperts servers, all e-mail is filtered as it should be. Please note that you will be responsible yourself for changes in IP addresses. Of course, Openprovider informs you about this on beforehand.
To make it easier you can also make your MX records point to a CNAME to primary.mail.registrar.eu and fallback.mail.registrar.eu. This way you will have whitelabel, but not the responsibility of updating your records!