A Guide to Centralized Spam and Virus Filtering

Spam and viruses constitute an enormous amount of mail on the Internet, wasting bandwidth and clogging the queues on defenseless mail servers. If delivered, the viruses also waste company resources as they spread. Mail administrators have taken a variety of approaches to defending their users from these two culprits, but it's difficult to keep up with new techniques and viruses and worms. This article explores the integration of Sendmail, MIMEDefang, ClamAV, SpamAssassin, and Vipul's Razor as a partial measure against spam and viruses.

On a machine running traditional Sendmail with no modifications, mail enters the machine via an SMTP transaction on port 25, is processed by the mail transfer agent or MTA (Sendmail) and is then handed off to the local delivery agent to be stored on disk for retrieval by the user.

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