On May 13, J.T. Conklin wrote
> We recently added a domain blacklist (thanks to qmail's way-cool
> badmailfrom feature) which protects the lists against known spammers.
> Unfortunately, it won't catch new spammers.  We'll try to keep the
> blacklist as up-to-date as possible, but it is likely that some 
> spam is going to slip through nonetheless.
> 

One way to efficiently filter spams is to reject the mail if domain specified
in the SMTP "mail from:" command doesn't have a DNS entry. This works
for most spams with forged adresses. The error message must be a 4xx, so
that a temporary DNS failure won't definitively reject valid mails.

I have this on my mail server, seems to work fine. Don't know if this
is easy to do with qmail ...

--
Manuel Bouyer, LIP6, Universite Paris VI.                 bouyer@masi.ibp.fr
     {Net,Free}BSD: 21 ans d'experience feront toujours la difference
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