BoxTrapper protects your inbox from spam by requiring all email senders, not on your Whitelist reply to a verification email before you can receive their mail.
Warning: Users will need to keep an eye on their BoxTrapper Queues to ensure that mail they wish to receive is not trapped.
You can manage this by visiting cPanel > BoxTrapper. You need to configure it for an individual email address. Simply click on "Manage" from functions. You can enable it by clicking on Enable button from the next page. You can configure as per your necessity from options in this page.
It is highly recommended that you use Apache SpamAssassin in conjunction with BoxTrapper as it will reduce loads on the server and backscatter to illegitimate email addresses.