Milter-greylist

I wrote:
>> However, you would never want to block them outright, since
>> they're not known spammers (yet).  By delaying their mail, you
>> give the blacklists time to receive reports, and then
>> Spamassassin can kill them when it checks those blacklists.

Mart Pirita wrote:
> How many legal email have You received from these not know spammers
> yet? I presume none. Usually, if they appear in blacklist, their 
> administrator tries soon to release from there. It can take less
> time then greylisting them in Your server.

My script extrapolates data, creating a buffer around spammer IPs.
The IP blocks are not *entirely* composed of blacklisted addresses,
therefore this is not a blacklist.  I'm not going to block somebody
because they are in China or Poland and their neighbors are spammers.

Plus, as shuttlebox/peter points out, the time/resources it requires
to greylist is roughly equivalent to a rejection, which I typically
regard as a free operation.  It's running through spamassassin and
clamav that consume resources.