Chapter 9. Email Client Filtering

This chapter covers a few of the tools available to mail clients in the fight against spam. These filtering tools and techniques (with the possible exception of POPFile) are meant to complement the coverage of the anti-spam methods outlined in this book. These tools are meant to show the reader how to use the client-side techniques with the server-side methods covered in other parts of the book. Although the focus of this chapter is on Microsoft Windows, these techniques can also be applied to other platforms where the applications have been ported to run (for example, Mozilla Messenger on Linux).

In this chapter, we cover the following email clients and related software:

• POPFile v0.21.1 POPFile is a powerful multi-platform POP3 proxy written in Perl that implements the Bayesian classification algorithm. It works very well, but only with POP3 accounts. (IMAP and other protocols are planned for a future release.)

• Mozilla Messenger 1.6 Mozilla has excellent message filtering and a rudimentary Bayesian classification implementation. It enables you to have the benefit of a modern Bayesian anti-spam implementation integrated with an email client.

• Microsoft Outlook Express 6 Outlook Express's support for filtering messages is limited to subject line modification. There is no other anti-spam capability within the package.

• Microsoft Outlook 2003 Outlook has excellent support for filtering messages and some capability for dealing with spam messages via its Junk E-Mail Filter With Microsoft SmartScreen Technology. Plugins are available that extend Outlook to have integrated Bayesian filtering capability.

The topic of Procmail filtering was covered in Chapter 2, "Procmail," so please refer to that chapter if you are interested in performing filtering "outside" an email client covered here.

The choice of which email client to use is usually a matter of (your or your customer's) personal preference. For the client portions of this chapter, you should pay close attention to the sections of the chapter that cover the clients that you or your customer(s) use. POPFile could be of great use to anyone using any compatible email client (a client that supports the POP3 protocol).