Many email administrators are happy with the operation of their email server, but still want to add spam filtering. If the current email server is running Windows, then integrating SpamAssassin into Microsoft Exchange Server is difficult and perceived as risky. This is because it may be difficult to revert to the old settings due to the way in which some settings are changed. Whatever the platform, email administrators who lack formal training or do not devote a considerable amount of their time to system administration might lack the confidence to alter the configuration of a running email server.

One safe solution is to use a separate email gateway. The gateway receives all incoming email, SpamAssassin identifies and tags spam, and then emails are forwarded to the original email server. The gateway can additionally provide spam filtering, if desired, and forward spam to a different account or simply delete it. The configuration of the existing server...