I never recommended wholesale blocking of all DSL lines. In fact, I even stated that I myself used an SDSL line! See Mike K's well written response to your post. He hit the nail on the head. You are putting words in my mouth that I never used, nor would I use. This is about RDNS/IP issues, not the method of transport itself...
It *is* about the method of transport. It's kind of like saying "My business doesn't discriminate against the poor, but we do require payment by credit card" -- the two are closely enough related that one has the same effect as the other. If you require credit cards, you're discriminating against the poor, no matter how nice you are to poor people or what your policy may say.
Along the same lines, if you say you do not recommend blocking DSL lines, but you recommend blocking non-vanity reverse DNS entries, then you are recommending blocking DSL lines.
You say it is an RDNS/IP issue, but it isn't (it's a static vs. dynamic issue). The problem is that you are getting spam from dynamic IPs (not that you are getting spam from IPs with non-vanity reverse DNS). So why not block dynamic IPs? Because you can't. Len can't. MAPS can't, SORBS can't. So you switch from "I'm blocking dynamic IPs" to "I'm blocking non-vanity reverse DNS entries." Why? Because you can.
Why not just take the HELO/EHLO, and [1] Check to see if it has an IP in it; if so, block the mail, and [2] If no IP in it, do an A record lookup to see if it matches the IP connecting to you? It solves your problem, and reduces the false positives.
Quite honestly, if a commercial ADSL line is set up and labeled properly, I would never know whether it was ADSL, a T1 or an OC3.
That's the problem with your spam test. You can't tell what kind of connection someone has from their reverse DNS entry. Since you can't tell what kind of connection they have, using the reverse DNS entry to try to block specific types of connections won't work.
I don't mind when people say they have a great spam test if they mention the flaws. If they do not mention the flaws, well, I'm happy to point them out. <G>
-Scott
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