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How To Fight Spam Using Your Postfix Configuration
hausmasta writes, "In this guide you will learn how to tweak your virtual Postfix setup to better combat spam by stopping the mail before it hits SpamAssasin, using RBL (Realtime Blacklists) and RHBL (slightly different), greylistings, and Helo Checks." A clear, step-by-step guide to a complex subject.
We block somewhere around 200k spam emails a day. And we have a very similar setup sitting in front of our Exchange server. The kinds of things we can do with Postfix simply aren't possible with Exchange, and once we learned the ins and outs of Postfix, we found it to be easier to use than Exchange. For one, Postfix has real documentation. Not to mention that the main developer posts regularly on the mailing list. Ever talk to MS's corporate support people for Exchange? Exchange is so huge and complex no one person knows the entire program. Postfix is a model of simplicity by comparison.
As someone who uses Exchange I can say that setting spam filtering up is easy. You can use RBLs or not. You can set thresholds that let a lot in or block a lot with many false positives. If you're worried about losing business mail then you can configure it to be safe about that and never outright refuse or delete mail.
But I don't like it because once you check the boxes, set the sliders and press OK, that's it. Unless you then get into scripting or third party products or any other solutions I can't think of you don't get to customize it any further. In other words, at that point, if you want more, it's just like Unix. I've never worked with any but can't you buy Sendmail or OpenExchange and get a lot of the point and click stuff for free too? And for a lot less then the dragon's horde a small business spends on MS Exchange?
One last thing to mention, we feel the same way as you about losing a customer's mail. So our users don't get anywhere near the spam they used to but the IT Admin that works for me spends anywhere from an hour to two a day checking the spam filter to see what gets tagged. Whitelisting? So far we found a few half ass solutions in forums that for various reasons don't do exactly what we need.
All in all, like most Window's based solutions in my experience, Exchange is easy to set up, hard to customize. We're working on a OpenBSD solution as a front end in our spare time. Hopefully we can get it to get the worst of the spam and then set Exchange to be a lot more lax when it gets in... Anything that keeps us from checking the spam filter all day.
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I'm having excellent luck with OpenBSD's spamd blacklisting and greylisting. Haven't lost any important mail, but my SPAM has been cut by about 98%. It's truly amazing.
http://www.openbsd.org/spamd/
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