3.1 Amavis as a Postfix Before Queue Filter
As mentioned in Section 2.1, amavisd-new is configured as a pass-through filtering proxy for the Postfix server. It serves as a “before-queue” content filter that scans messages for spam and viruses before they are added to the Postfix mail queue for cleanup and distribution. Amavisd-new provides a consistent infrastructure for screening incoming mail for undesirable content. Currently, amavis-new is set up to check for viruses with ClamAv and weed out spam with SpamAssassin. External spam filtering services, Razor and DCC, assist SpamAssassin in this task. Figure 4 illustrates the relationship between these components.