You can add anti-spam capability to an email infrastructure in many ways. In this section, we show two hypothetical examples. We start off with a simple configuration that a small enterprise might use. This system contains a single overloaded machine running all mail services for the organization. We finish the chapter by showing how a larger organization might deploy an open source anti-spam solution on its network.
In a case where the existing email infrastructure is overloaded, it is usually best to add a dedicated machine that handles anti-spam and mail relay functions. The addition of a resource-intensive application such as SpamAssassin will simply put too much load on the existing servers.