Milter-greylist

>1) black lists are not reliable

The passage I quoted from http://hcpnet.free.fr/milter-greylist/ assumes use 
of a black list. I'm simply proposing a fuller and more sensible use.

If a black list contains legit sender addresses, I would think there's 
something wrong with the black list provider, not with the concept of black 
lists.

>3) deleting mail is dangerous.

Ditto my reply to #1.

>2) your idea woks only if the mail is hold on the mail server. What if it 
>has been forwarded to another machine?

My idea is an idea for killing SOME spam before it reaches the target. It 
works for that. It doesn't claim to stop all spam.

Of course a particular machine can get the black list info too late. They 
can all get it after the user has already retrieved the spam. Stuff happens. 
I'm just proposing that mail servers not ignore the spam they're already 
sitting on when they learn of a new spammer.