For a lot of us these days, “control” of email is more of a sad joke than a reality. New laws may not do much to stop the flood of spam, and viruses and worms keep sneaking in. As incoming messages make your server struggle and users’ inboxes groan, what’s an administrator — or a user — to do?
For a lot of us these days, “control” of email is more of a sad joke than a reality. New laws may not do much to stop the flood of spam, and viruses and worms keep sneaking in. As incoming messages make your server struggle and users’ inboxes groan, what’s an administrator — or a user — to do?
System-level mail filtering can help, but it’s not always the best answer. For instance, blacklisting entire domains (refusing messages from certain servers) can mean that you miss email from potential customers — customers who don’t know (or care) that their postmaster isn’t following proper anti-spam procedures. Or a colleague of yours might keep sending late-night emails, asking you for a date, and you’d like to trash those messages automatically, but still receive his other, business-related messages.
This month, we’ll look at ways to filter mail using procmail (covered in several recent issues of Linux Magazine, as well as at http://www.procmail.org), emphasizing ways to detect messages using the contents of the header or body of email messages. (Some of these same techniques also apply to other mail-filtering systems.) Let’s get digging for that dirt!
What’s the Problem?
One of the first steps to take when you want to filter mail is to see as much of each message as you can. Many mail user agents (MUAs) like Outlook Express don’t show what’s actually in the message header and body. (The article “Personal Post,” available online at…
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