It is a general purpose naïve bayesian email classifier that you can integrate with almost any email system.
They took some of the concepts in the article mentioned here and expanded on them a bit.
For example, they have the idea of "pseudowords"[1] so that you're working with more than just the words in the email. Like html:td for example...it expands to the number html table cells in an email, which might help with choosing a bucket.