Get a bunch of Linux professionals together these days and the topic inevitably turns to the spam problem. How much do you get, how many sneak through your filters and, of course, what are the bad things that happened to you when a spam filter decided to eat some important legitimate mail at the worst possible time.

If you're just getting your personal e-mail via POP or IMAP, spam might merely slow you down. But when you manage mail for a lot of users it's now a major cost. A flood of unsolicited bulk e-mail actually made an entire university's e-mail system obsolete. The bad news is that spam unfairly shifts the cost of marketing from senders to recipients. The good news is that Ludovic Marcotte's team made that cost as low as possible by deploying a reliable all-open-source mail system on Linux and commodity hardware. When you read the success story on page 44, notice that the site has planned to add more machines as the spam problem gets worse.

But there is hope for the spam problem to get better in the future. We won't go quite as ga-ga with “the end of spam is coming” predictions as some tech CTOs, but we can make spamming less lucrative for the perpetrators and maybe just another Net nuisance.

SPF fights forged spam by giving other sites' mail servers a way to check whether mail is really from you. Meng Weng Wong covered how to label your mail server as legit in our last issue, and now it's time to collect the benefits. Follow the steps in both articles and you'll quickly block out all the spam that claims to be from your own domain, then get more effective protection as more sites use SPF. If you're joining us in the middle, there's a link to the Web version of Part I.

System administration isn't all fun, glamour and beating back hordes of slavering spammers to the sounds of cheers and sighs of gratitude from spam-free users. So don't worry—we cover the important behind-the-scenes tools in this issue too. Now, time is only unidirectional in Stephen Hawking movies and reality. On your RPM-based Linux system, you can go back in time to correct a good upgrade gone bad. James Olin Oden describes how to do transactions and rollback with RPM on page 40.

If you want to get every last bit of the bandwidth you paid for, but not go over and hit steeper charges, check out the article by David Mandelstam and Nenad Corbic on page 54. Now you easily can make your Net traffic use whichever connection makes sense and use low-priced, small-business connections, such as DSL and cable modems, where you can.

Let's just take a moment to give thanks for the spammers while we have them. Think about it—we've learned to do groovy text classifying math, we've developed knowledge of the SMTP protocol and where future protocols can be better, and we've given users a new appreciation of where they would be without system administrators. Thanks, spammers.

Actually, no, on second thought, let's just put the parasites out of business. Enjoy the issue.