transcyberia.info - email

the spam arms race

nospam@example.com (Guido Stevens) — Mon, 02 Jun 2008 14:53:00 +0200

The war on spam is mostly waged between spammers and ISP's, invisible to the public.

Earlier I wrote about greylisting. That's a fairly minimal change in handling email, that reduces the spam volume on our mail servers disproportionately. How can this be? Let's take a look at the economics involved.

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fighting spam with greylisting

nospam@example.com (Guido Stevens) — Fri, 23 May 2008 16:51:00 +0200

At the NFG mail servers, we block about 10 spam messages for every valid email our customers receive. Even so, customers keep asking for more agressive spam filters.

Spam filtering requires a lot of system resources. Content filtering involves opening each message and matching its full contents against a database of spam patterns. This involves a lot of disk read/write actions and heavy number crunching.

In the graph above, our mail server was flooded with more spam than it could adequately handle. Of course, we could allocate more system resources or try and tune the server some more. However, the solution turned out to be much simpler: greylisting.

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interfacing with the DBMail database

nospam@example.com (Guido Stevens) — Tue, 20 May 2008 11:34:07 +0200

Paul and myself have started a new DBMail blog.

Read the full blog entry @blog.dbmail.eu about direct database access versus protocol-mediated data retrieval.