== A temptation with challenge/response anti-spam systems

Every time I see a mail from a C/R system, I get more and more tempted
to teach our mail filtering infrastructure about the most common ones,
so that it can automatically acknowledge the challenges, discard the
messages, and not bother the users with them at all.

Will this acknowledge a lot of spam, and thus dump it on the people
operating those C/R systems? Sure, but that's not *our* problem. And
I'd clearly be doing our users a service, especially if C/R systems get
widespread.

(This is [[another example CRProblem]] of how C/R systems try to work by
offloading your spam problem on precisely the wrong people. The only way
they can 'work' at all is if most of the mail addresses you challenge
don't even exist; otherwise you are reaching either spammers or pissed
off people, neither of which have *your* interests in mind.)

As a special bonus prize, I could even hack our system to do this even
for local addresses that don't actually exist, since it's perfectly
possible to automatically acknowledge the challenge *and* 5xx the _DATA_
command at the end of the SMTP conversation. I'd have to make sure that
this only happened for single-recipient email, but that describes all
of the C/R email I'd want to do this to.

(Ob-attribution-darnit: I've had this thought for a while,
but the impetus to actually write this entry was provided by
reading about a related temptation with C/R systems [[here
http://solipsistnation.livejournal.com/401711.html]].)