Slashdot Mirror


Are SPAM Blacklists Unreasonable?

rlsnyder asks: "I'm the inadvertant co-administrator of e-mail a for company that relies pretty heavily on it for daily business (e.g. sending confirmations of financial transactions). At one point in the not-too-distant past, our server was an open relay. I admit I'm a sinner for letting it happen, and I'm ready to do my pennance. Given the relatively low volume of mail our server moved that did not originate from inside, I doubt I was a major contributor to the world of SPAM. In any event, we've been blacklisted on a number of sites. Some lists have reasonable policies, and we've since been removed. Other places are a little more arbitrary as to removal policies, and although I can prove we're not a relay, we're still listed." While I approve of the basic concept of SPAM Blacklists, there are dozens of SPAM blacklists out there who are real keen on adding open relays to the list, but not so keen on taking rehabilitated hosts out. I would posit that SPAM blacklists that are not properly maintained are a part of the problem, not the solution. What are your thoughts on the subject?

rlsynder continues: "Am I way off base here, or is this self-appointed mail police thing going in the wrong direction? Given that I can't reliably deliver e-mail to a number of places due to being blocked, I've got a big exposure. Is this making spam less of a problem, or are we trading one problem (SPAM) for another (the reliablility of proper maintenance of SPAM Blacklists)?

I could draw a bunch of analogies here, but isn't the bottom line that no one owns the internet e-mail system? I realize no one makes ISP's subscribe to the blacklists, but basically, I'm trying to move data from one point to another, and some machines in the middle are discriminating against my data because a corrected, perfectly legal system configuration error. How is this helping? Has SPAM really decreased universally thanks to these lists?"

2 of 619 comments (clear)

  1. Shout out for SpamAssassin by dietz · · Score: 5, Informative

    I'd just like to give some props for SpamAssassin.

    If you haven't heard of it, it's an elegant system that assigns a weight to each email message based on hundreds of different tests, and if the email scores over 5 (configurable), it is marked as spam.

    One of the nice things about it that is it uses most of the email blacklists, but they're only worth ~2 points, so being in a blacklist alone isn't enough to kill a message. That's good for those blacklists that throw far too many people in that don't belong (osirusoft). It also uses razor, but that is only worth three points, so if someone is piping bugtraq to razor-report (that happened for a while) you won't lose all that email.

    There's a really interesting set of tests (it's fun to read them) each with an obscure set of points including:
    HTML with a non-white bgcolor (1.2)
    Claims conformance to obscure spam law (1.0)
    HTML mail with no text portion (3.33)
    Various spam phrases (various points depending on how many "hits" there are)
    Subject ends in an exclamation point (0.5)

    The points have apparently been calculated using some program to give the best accuracy.

    Anyway, SpamAssassin is the best of the spam removal programs I've seen. Give it a shot!

  2. Protecting my server, thank you very much by alansz · · Score: 5, Informative
    DNS-based blacklists are not your problem. There are no more than a dozen that are really widely used (some orbs spinoffs like http://www.ordb.org and http://www.orbz.org, the MAPS ones if you're willing to pay (or can get a hobby contract) at http://www.mail-abuse.org, and the collection at http://relays.osirusoft.com that includes open relays, spamhaus, and SPEWS. All of these systems have clearly-published listing policies and are actively maintained and if you're blocked by one of them, you'll likely get out sooner or later once you're clean. (In some cases, you can have them automatically retest you). Plenty of mail admins find that using the information on these sites to protect their mail servers from spam is highly effective.

    Your problem is twofold. First, while you've cleaned up your open relay, plenty of spammers and spam-friendly hosts make the same claim and lie (Rule #1: Spammers lie). So you may have to be patient.

    More importantly, your server ip may now be sitting in hundreds of private blacklists of mail servers whose admins don't like to use the centralized lists, and just reject/blackhole spammers on their own. It is the presence of well-trusted centralized blacklist services that gives you even the hope of ever having decent communication, because without them, you'd get into a thousand tiny blacklists and never get out.

    (P.S. Note that if you're checking your status using the rblcheck tool at http://relays.osirusoft.com, it will tell you about a lot of blacklists that are not intended to be publicly used and not part of the usual osirusoft dnsbl, as well...)