Ralf Hildebrandt a écrit :
> * Gábor Lénárt <[email protected]>:
>
>>> This is a backscatter source and will get you blacklisted in no time.
>> Hmm, what would be if someone use a policy server, rejecting the mail with
>> the link for the captcha URL in it.
>
> That sound interesting. It could work! It definitely solves the
> backscatter issue.
>
Error messages may be "translated" by the final server (so your nice
"blah blah see http://.... blah blah" may become "mailbox unavailable:
error 501"). in general, smtp errors are not guaranteed to arrive to the
original sender.
anyway, challenge-response is a bad idea. do not delegate your spam
filtering to others. not only it is selfish, but it is unreliable:
If I get a challenge from someone I've never sent mail to, I do verify
the challenge, so that he gets spam. (false negative)
If I get a challenge from someone whom I sent mail to, I don't verify.
so that he misses my email. (false positive). depening on the situation,
I phone the recipient claiming that I saw no response (did I see a
challenge? ;-p).
for more infos, see
http://spamlinks.net/filter-cr.htm
as well as google...
