Once another spam filter has been selected, it should be integrated into the existing email system. In this chapter, two configurations are discussed. In both cases, the additional spam filter will be used first, reducing the number of emails that reach SpamAssassin.
The two configurations considered here are to run the new mail filter on the existing machine, or to use an additional machine solely for running the new spam filter.
Using two machines gives an advantage in terms of raw processing power, but introduces an extra point of failure. Additionally, configuration may be far more complex. For disaster recovery or hot fail-over, the cost to add one machine is doubled.
The two approaches have different strengths and weaknesses. The decision should be made based on the current system load, and the backup/disaster recovery strategy in place.
