Promising antispam technique gets nod

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Doing that, works great!

My Postfix tests for valid PTR and A records. MX records are not required and you'll get a ton of false positives if you test for them. The PTR+A test is the most productive single test in my arsenal. Stops 75% of incoming spam and I recommend the technique. But if everyone did it the spammers would just stop sending from places without those resource records. And there are enough false positives with PTR+A that I have to give a URL in the rejection message and whitelist a legitimate sender with broken DNS every few weeks. I doubt a big ISP would get away with it long enough to force the world to clean up its broken DNS.

Most of my spam comes from compromised "small business" email servers these days. Most of them Microsoft, of course. These servers all have valid Address and PoinTeR records.

Cameron

http://spam-vs-freedom.blogspot.com

Posted by: cls@...   Posted on: 05/23/07 You are currently: a Guest | Members login | Terms of Use

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