Spam Challenge-Response system

Jonathan Ellis jonathan at
Fri Apr 10 09:45:55 MDT 2009

This idea was fairly popular a few years ago but has mostly been
dropped since other methods that aren't so annoying for non-spammers
do a pretty good job.

But some people are still working on them, e.g.

On Thu, Apr 9, 2009 at 1:35 PM, Jessie Morris
<jessie at> wrote:
> I was wondering if there was any way that I could make my mail system respond
> to emails received with a link that says something to the effect of, "If you're
> a human, click here to be allowed." I've done some searching on Google, and
> haven't found a really good system. Ideas?
> --
> Jessie Morris
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