And that is probably just fine, as 99% of the true spam comes from email addresses (and often doamins) that either do not exist, or often are not configured to receive email.
I call BS. I ran sender-callout verification on my primary email server for a while (before I became convinced it was mildly abusive, and stopped) and typically blocked 2-3 spams per day. In fact, I had more FPs than legit spam blocked by that method.
If you didn't send the the email, why bother confirming it? Aren't you also adding back to the problem?
Absolutely I am. If you're going to try to offload your spam filtering to me, I want the process to cause you as much pain as possible (within ethical limits, which is why I won't forward your email
Even if you confirm your email address, that's all that spamarrest is asking for. If the email address is valid, then it's done its job.
Sender callouts will verify addresses without requiring any action from the end user. If you must [ab]use my resources to do your job, please have the common decency to use my (abundant) hardware and software resources rather than my (much more limited) wetware resources. -- Dave Pooser, ACSA Manager of Information Services Alford Media http://www.alfordmedia.com