rejecting spam at SMTP time (was Re: Postfix anti-antivirus (was Re: [linux-elitists] etc))

Andrew Kohlsmith
Fri Oct 1 07:20:05 PDT 2004

On Tuesday 28 September 2004 15:31, Rob McGee wrote:
> Spamhaus XBL includes the CBL. is indeed a very
> good choice for conservative spam filtering. I've been using it only a
> couple days, still watching logs closely, but the few it caught did
> definitely sound like spam ... if you can judge from the envelope:
> something like coming from Portugal, for
> example.

This is where SPF comes in handy; unless that Portugese server is allowed to 
send mail on's behalf it wouldn't get through.  I just hate the 
additional network traffic involved in checking SPF records; that is why I 
use rsync and build the RBL lists locally to try and keep the total amount of 
network traffic down and the actual SMTP-time lag low.

> For some sites I'm going to get more aggressive than that and use
> dynamic IP blocks. I feel like a hypocrite in doing so since those
> lists used to block ME, but unfortunately it seems to be a very strong
> antispam measure.

Agreed; It's a shame that things have to get this way but until the spam 
problem is able to be better addressed though simple, fast and low-traffic 
verification of the sender and its authority to send on the behalf of the 
domain it's claiming to send from...  we have little choice.    It's just an 
arms race.


More information about the linux-elitists mailing list