On Fri, Dec 02, 2005 at 02:23:00AM +0100, mouss wrote:
> if you block at IP level, and if sender client is an MTA, it 
> will retry.  

Uh? Only on DEFER (4xx), on REJECTs (5xx) the MTA is not supposed to retry.

> To avoid listing ISPs, he could only list those clients wich 
> name looks dynamic. for instance, restrict to when hostname 
> matches /\d\d\d-\d/. (I am meaning to limit damages, not to say 
> that this pattern implies a dynamic client. it is still possible 
> to have an isp mailer named "outmail-212-3" if it's the 3d 
> mailer for some "212" block...)

That or use reject_rbl_client with proper RBLs. That's actually the same like
his idea, but _humanly_ verified (if it is a good RBL). I would very avoid
RBLs which use automatic mechanisms unless they are failproof. Spamtraps are
not.

Alternatively he could use greylisting (by avoiding greylisting real MTAs)
or policyd-weight.
http://www.postfix.org/addon.html#policy

However, an automatic blacklisting out of logs is a very call for trouble.
Especially when it comes to forwarders and real MTAs (like ISPs).



-- 
    Robert Felber (PGP: 896CF30B)
    Munich, Germany


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