What is the VBSpam Challenge?

In their own words:

VBSpam comparative testing is a regular independent comparison of anti-spam solutions.

The aim of these tests is to offer readers the best impartial advice about anti-spam security and the products on offer.

By using a combination of two live spam streams representing mailboxes all over the world, as well as a live stream of legitimate international emails, the VBSpam test aims to reflect the experience of a real end-user as accurately as possible.