> Well it depends on the implementation my graylist blocks only first attempt
> form the e-amil adres/ip hash so if sombody sends a message again it goes
> through the db is kept for one month so only the first message is delayed :)
That's also how I have it configured - however, it's commonplace in business
to deal with new customers that have not sent you an e-mail before - so it's a
new address. This delay may be unsatisfactory in this case.
Imagine if you will, the client that calls my imaginary, ficticious company -
and during the course of the conversation I request him to e-mail me some
spreadsheet, so I can look at the figures that he has in front of him. Now I
have to hold him on the phone until his mailserver retries outside of the
configured hold-time on my greylisting mailserver. Depending on many things,
that might not be for hours.
Greylisting is a very useful hack - but that's all it is. When I configured
it on skynet it brought the spam levels down to maybe 1.5 a week, for a while.
They are now steadily climbing again.
For me, a real frustration is also websites that require me to sign in,
provide a real e-mail address and then, before I'm allowed to continue, I need
to provide an authentication code or something from the e-mail I've just sent
them. With greylisting, the wait to receive that authentication code can be of
the order of hours, meaning I'm unable to progress for that period of time.
So, in summary, greylisting is an extremely useful tool for fighting spam -
but it is only one of a set that should be used and is not a perfect solution
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