Re: [opensuse] Can spam be defeated?
- From: Daniel Bauer <linux@xxxxxxxxxxxxxxxx>
- Date: Thu, 21 Dec 2006 12:03:32 +0100
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
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