[Mailman-Users] Spam to list-owner

Lindsay Haisley fmouse-mailman at fmp.com
Sat Dec 20 17:41:15 CET 2008

On Sat, 2008-12-20 at 19:35 +0900, Stephen J. Turnbull wrote:
>  > Courier doesn't need milters.  Maildrop can be run in what's called
>  > "embedded mode" which is effectively the same thing.
> x`
> No, it's not the same, not for the purpose of deciding whether
> *Courier* needs milters.

A "milter" is just an MTA component/plugin that reflects user-space
(outside the MTA) decisions on spam/viruses back to the SMTP dialog so
that a receiving server can reject an email for cause without generating
a backscatter email to the envelope sender.  Maildrop in embedded mode
_is_ a milter - a highly programmable one.  Using maildrop, an email can
be fed to any program for analysis - shell script, SpamAssassin, etc. -
which need not be SMTP-aware, and the output and exit code of said
program can be used to determine the course of an SMTP session.

Yes, it's desirable when possible to reject problem email at the front
door, but it's not a religion with me.  I've done my time in the
spam-fighting trenches, probably more than most mail admins.  I do
understand email pretty well, and know how to implement decisions I make
about how to handle problem email.  It's just these decisions are
probably not the same ones you'd make.  

I'm not going to change my fundamental decisions on how I handle problem
emails on my system, which aren't doctrinaire and may not be
e-politically-correct by some standards, but I've kept this thread going
because I rather selfishly find that occasionally someone tosses out a
Good Idea that I may be able to use :-)

BTW, as I mentioned, about 80% of the spam _I_ (personally) get is
rejected by courier based on RBL lookups, and I assume the percentage is
similar for other system users.  I have a cron job which generates a
daily report on these rejections for me, and anyone else who wants one.
The number of rejections I see in the report for my personal email
varies between about 200 and 800 or so a day, and has remained in this
range for several years.  Frankly, I don't believe rejecting an SMTP
transaction out front makes one whit of difference to spammers, and I've
seen no arguments to indicate that it does.  A huge amount of this spew
comes from Asia, Russia, South America, and my guess is that it's either
coming from virally infected / hacked boxes or from rogue servers that
crank out terabytes of this crap, and in any case the people sending it
don't give a damn whether any particular target (victim!) system rejects
1% or 99% of it.  

It's just that, by rejecting this stuff out front, one gets the visceral
satisfaction of knowing that some spammer, somewhere _might_ be annoyed
or inconvenienced by seeing the bounce notices from their server.  I've
heard all the arguments about CPU usage and system load involved in
accepting and processing spam, but my service is a relatively small one
and my system load generally runs under 1.0, even with all that spam
coming in :)

Lindsay Haisley       | "Everything works    |     PGP public key
FMP Computer Services |       if you let it" |      available at
512-259-1190          |    (The Roadie)      | http://pubkeys.fmp.com
http://www.fmp.com    |                      |

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