Researchers at Virus Bulletin have written about a theoretical technique for improving spam filtering: combining the action of several filters.
The researchers sent about 200,000 emails to 14 anti-spam products. No legitimate email was blocked by more than four of the 14. They suggested that a hypothetical filter that tagged an email as spam if five or more of the 14 called it spam would result in 99.89 percent successful filtering with no false positives.
Their conclusion is that enterprises might consider using more than one anti-spam product and anti-spam vendors might consider sharing information.
At Sunbelt we have been doing this for a while. In our VIPRE Email Security for Exchange enterprise software solution we use the Cloudmark antispam engine and the Mail-filters engine as well as Real-time blackhole lists.
Info on VIPRE for Exchange here.
VB story here.