If you have purchased a Professional Spam Filter account, and also host your mail using a cPanel/WHM server, you can have the "Professional Spam Filter" plugin setup for easy protection of mail services.
Note: the below will only work effectively, if you are using your server for DNS Hosting! If you are not, you will need to manually update your MX records remotely.
To Access, and protect a domain with this plugin setup, you would login to WebHost Manager, and follow the below steps.
Search for "Professional Spam Filter" within the sidebar of WHM.
Click on the plugin, and it will take you to an overview page. Select the "Domain List" in order to view a list of all of your domains.
Once on the next page, you can search for the domain you would like to protect.
If you click on "Check Status", it will check and see if you are protected within the filter
If you then click "Toggle Protection", it will add the domain to your SpamFiltering account, and make any DNS changes required to point it via the Spam Filter.
The same method works, for deleting an account from your spam filter, if it's no longer required. In general, if a cPanel account is deleted, it will also automatically be removed from the filter service.