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List:       opensuse
Subject:    Re: [opensuse] Can spam be defeated?
From:       Daniel Bauer <linux () daniel-bauer ! com>
Date:       2006-12-21 11:03:32
Message-ID: 200612211203.32488.linux () daniel-bauer ! com
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On Thursday 21 December 2006 11:26, Sandy Drobic wrote:
> John Andersen wrote:
> > On Wednesday 20 December 2006 23:37, Joachim Kieferle wrote:
> >> IF BY ACCIDENT a mail is blocked, the positive effect from that is, that
> >> the senders are informed about blocking (e.g. Blocked - see
> >> http://cbl.abuseat.org/lookup.cgi?ip=82.197.44.218), whereas
> >> SpamAssassin "just" marks the spam and one tends to delete the spam
> >> without even reading the header / sender.
> >
> > Whoa there big fella!
> >
> > You are ADDING to the PROBLEM by generating backscatter, and
> > probably joe jobbing some poor schmuck who the spammer
> > pretended to be.
>
> Wrong. The mail is not accepted and instead REJECTED during the smtp
> dialogue. The responsibility for the mail remains with the sending client.
> May that be the spammer or a normal mailserver.
>
> Dec 17 04:52:12 spamkill postfix/smtpd[18477]: NOQUEUE: reject: RCPT from
> customer.optindirectmail.83.sls-hosting.com[204.14.1.83]: 554 5.7.1
> Service unavailable; Client host [204.14.1.83] blocked using
> zen.spamhaus.org; http://www.spamhaus.org/SBL/sbl.lasso?query=SBL27197;
>
> Opt-in, yeah, sure...
>
> Not even a queue file has been created yet. That is exactly the difference
> to the normal use of amavisd-new or spamassassin: that filtering happens
> after you accepted the mail, so you can't reject the mail at that stage.
> At that point you can only tag-and-deliver.
>
> The biggest problem on the corporate side are gateway mailserver that
> accept a mail without knowing if the recipient is even valid. They try to
> relay the mail to the internal exchange server which is then telling them
> the recipient is invalid. Then they bounce the mail back to the, in case
> of spam forged, sender address. That is the backscatter we all know and
> love. :-((
>
> Sandy

I am not at all an expert, but I dislike the option of rejecting emails due to 
a blacklist. I prefer to have spam in my spam-folder (after it has been 
marked by Spam-Assassin), where I can quickly overview the subject lines.

Some years ago my (old) ISP started rejecting e-mails using a blacklist. At 
that moment one of the lagest german ISP's ("Schlund+Partner" and its 
numerous sub-companies) was blacklisted. I suddenly had no more business 
contacts to Germany anymore and it took quite a while for me to find out 
why... The ISP told me, I should write to my business partners that they 
shall change their ISP. This sounded like a joke to me, as many of my 
partners are quite large companies and their IT staff for sure is much more 
experienced than I am. In the end I changed to another ISP that let *me* 
decide from whom I want to receive mail or not.

Using blacklists for warning/marking purposes seems ok to me, but letting a 
blacklist make decisions can be dangerous. Just my opinion.

Daniel
-- 
Daniel Bauer photographer Basel Switzerland
professional photography: http://www.daniel-bauer.com
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