Milter-greylist

Hi,

we have some Perl script for this, showing that for the last
month 68 % of all delivered external mail came through immediately,
75% after 15 minutes, and almost 90% by 2 hours

but

the real problem for good senders is a configuration where
mail is sent only once or from different hosts where greylisting
prohibits delivery at all. I think you are lost if you
concentrate on clients with long delays.

We try to augment our whitelist by searching for mail hosts we
can trust in our domain. Regular expressions are useful for this.
We impose higher delays on hosts with no DNS entry at all and
those known in DNS black lists and with obvious DSL/IP names.
Then we look at those which are delayed by our minimal delay
time of 6 minutes and try to identify those we can trust.
Some simple pipe like
grep 'delayed for 00:06:0' /var/log/mail | cut --delimiter=' ' -f9 | sort | uniq
shows those where we can look for good arguments to put them
on the white list, like statistics of a different spam filter
(NiXspam in out case).

And not to forget customer complaints, which are - sometimes -
a hint for whitelist candidates.

Michael