BoxTrapper sounds good in theory, and maybe is good for those people who only get email from a few friends.
But, as soon as you start signing up for newsletters, or forums, or anything that sends out an automated email, you run into problems. BoxTrapper works with the assumption that it is a 'person' on the other end reading. And that's simply not the case.
Whitelisting is no good, because you don't know for sure what the address is that's coming in. And soon it becomes extra work to manually approve each automated email you want.Instead, use a good overall spam filter like MailScanner/SpamAssassin.