mirror of https://github.com/tLDP/LDP
784 lines
22 KiB
XML
784 lines
22 KiB
XML
<?xml version="1.0" encoding="ISO-8859-1"?>
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<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [
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<!ENTITY background SYSTEM "chapter-background.xml">
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<!ENTITY techniques SYSTEM "chapter-techniques.xml">
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<!ENTITY consider SYSTEM "chapter-considerations.xml">
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<!ENTITY qanda SYSTEM "chapter-qanda.xml">
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<!ENTITY exim SYSTEM "impl-exim.xml">
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<!ENTITY glossary SYSTEM "glossary.xml">
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<!ENTITY gpl SYSTEM "gpl.xml">
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]>
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<!-- "/usr/share/sgml/docbook/dtd/4.2/docbookx.dtd" -->
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<!-- "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" -->
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<book>
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<bookinfo>
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<title>Spam Filtering for Mail Exchangers</title>
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<subtitle>
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How to reject junk mail in incoming SMTP transactions.
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</subtitle>
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|
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<authorgroup>
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<author>
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<firstname>Tor</firstname>
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<surname>Slettnes</surname>
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<affiliation>
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<address><email>tor@slett.net</email></address>
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</affiliation>
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</author>
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|
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<editor>
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<firstname>Joost</firstname>
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<surname>De Cock</surname>
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<affiliation>
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<address><email>joost.decock (at) astrid.be</email></address>
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</affiliation>
|
|
<contrib>Technical Review</contrib>
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|
</editor>
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|
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<editor>
|
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<firstname>Devdas</firstname>
|
|
<surname>Bhagat</surname>
|
|
<affiliation>
|
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<address><email>devdas (at) dvb.homelinux.org</email></address>
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|
</affiliation>
|
|
<contrib>Technical Review</contrib>
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|
</editor>
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|
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<editor>
|
|
<firstname>Tom</firstname>
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|
<surname>Wright</surname>
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|
<affiliation>
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<address><email>tom (at) maladmin.com</email></address>
|
|
</affiliation>
|
|
<contrib>Language Review</contrib>
|
|
</editor>
|
|
</authorgroup>
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|
|
<edition>Version 1.0 -- Release</edition>
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|
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<keywordset>
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<keyword>anti-spam</keyword>
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<keyword>anti-virus</keyword>
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<keyword>bogus virus warnings</keyword>
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<keyword>collateral spam</keyword>
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<keyword>delivery status notification</keyword>
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<keyword>dsn</keyword>
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<keyword>exim</keyword>
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|
<keyword>exim4</keyword>
|
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<keyword>exiscan</keyword>
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<keyword>exiscan-acl</keyword>
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<keyword>greylisting</keyword>
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<keyword>junk mail</keyword>
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<keyword>sa-exim</keyword>
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<keyword>smtp</keyword>
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<keyword>spam</keyword>
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<keyword>spamassassin</keyword>
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<keyword>teergrubing</keyword>
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<keyword>transaction delay</keyword>
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</keywordset>
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</bookinfo>
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|
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<preface>
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<?dbhtml filename="introduction.html"?>
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<title>Introduction</title>
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<section id="purpose">
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<?dbhtml filename="intro-purpose.html"?>
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<title>Purpose of this Document</title>
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|
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<para>
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This document discusses various highly effective and low
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|
impact ways to weed out spam and malware during incoming SMTP
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transactions in a mail exchanger (MX host), with an added
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emphasis on eliminating so-called <xref linkend="colspam"/>.
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</para>
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|
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<para>
|
|
The discussions are conceptual in nature, but a sample
|
|
implementation is provided using the Exim MTA and other
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|
specific software tools. Miscellaneous other bigotry is
|
|
expressed throughout.
|
|
</para>
|
|
</section>
|
|
|
|
<section id="audience">
|
|
<?dbhtml filename="intro-audience.html"?>
|
|
<title>Audience</title>
|
|
|
|
<para>
|
|
The intended audience is mail system administrators, who are
|
|
already familiar with such acronyms as SMTP, MTA/MDA/MUA,
|
|
DNS/rDNS, and MX records. If you are an end user who is
|
|
looking for a spam filtering solution for your mail reader
|
|
(such as Evolution, Thunderbird, Mail.app or Outlook Express),
|
|
this document is <emphasis>not</emphasis> for you; but you may
|
|
wish to point the mail system administrator for your domain
|
|
(company, school, ISP...) to its existence.
|
|
</para>
|
|
</section>
|
|
|
|
<section id="updates">
|
|
<?dbhtml filename="intro-updates.html"?>
|
|
<title>New versions of this document</title>
|
|
|
|
<para>
|
|
The newest version of this document can be found at
|
|
<ulink url="http://slett.net/spam-filtering-for-mx/" />.
|
|
Please check back periodically for corrections and additions.
|
|
</para>
|
|
</section>
|
|
|
|
<section id="history" xreflabel="Revision History">
|
|
<?dbhtml filename="intro-history.html"?>
|
|
<title>Revision History</title>
|
|
|
|
<para>
|
|
<revhistory id="revhistory">
|
|
<revision>
|
|
<revnumber>1.0</revnumber>
|
|
<date>2004-09-08</date>
|
|
<authorinitials>TS</authorinitials>
|
|
<revremark>
|
|
First public release.
|
|
</revremark>
|
|
</revision>
|
|
|
|
<revision>
|
|
<revnumber>0.18</revnumber>
|
|
<date>2004-09-07</date>
|
|
<authorinitials>TS</authorinitials>
|
|
<revremark>
|
|
Incorporated second language review from Tom Wright.
|
|
</revremark>
|
|
</revision>
|
|
|
|
<revision>
|
|
<revnumber>0.17</revnumber>
|
|
<date>2004-09-06</date>
|
|
<authorinitials>TS</authorinitials>
|
|
<revremark>
|
|
Incorporated language review from Tom Wright.
|
|
</revremark>
|
|
</revision>
|
|
|
|
<revision>
|
|
<revnumber>0.16</revnumber>
|
|
<date>2004-08-13</date>
|
|
<authorinitials>TS</authorinitials>
|
|
<revremark>
|
|
Incorporated third round of changes from Devdas Bhagat.
|
|
</revremark>
|
|
</revision>
|
|
|
|
<revision>
|
|
<revnumber>0.15</revnumber>
|
|
<date>2004-08-04</date>
|
|
<authorinitials>TS</authorinitials>
|
|
<revremark>
|
|
Incorporated second round of changes from technical
|
|
review by Devdas Bhagat.
|
|
</revremark>
|
|
</revision>
|
|
|
|
<revision>
|
|
<revnumber>0.14</revnumber>
|
|
<date>2004-08-01</date>
|
|
<authorinitials>TS</authorinitials>
|
|
<revremark>
|
|
Incorporated technical review comments/corrections from
|
|
Devdas Bhagat.
|
|
</revremark>
|
|
</revision>
|
|
|
|
<revision>
|
|
<revnumber>0.13</revnumber>
|
|
<date>2004-08-01</date>
|
|
<authorinitials>TS</authorinitials>
|
|
<revremark>
|
|
Incorporated technical review from Joost De Cock.
|
|
</revremark>
|
|
</revision>
|
|
|
|
<revision>
|
|
<revnumber>0.12</revnumber>
|
|
<date>2004-07-27</date>
|
|
<authorinitials>TS</authorinitials>
|
|
<revremark>
|
|
Replaced "A Note on Controversies" with a more
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|
opinionated "The Good, The Bad, the Ugly" section. Also
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|
rewrote text on DNS blocklists. Some corrections from
|
|
Seymour J. Metz.
|
|
</revremark>
|
|
</revision>
|
|
|
|
<revision>
|
|
<revnumber>0.11</revnumber>
|
|
<date>2004-07-19</date>
|
|
<authorinitials>TS</authorinitials>
|
|
<revremark>
|
|
Incorporated comments from Rick Stewart on RMX++.
|
|
Swapped order of "Techniques" and "Considerations".
|
|
Minor typographic fixes in Exim implementation.
|
|
</revremark>
|
|
</revision>
|
|
|
|
<revision>
|
|
<revnumber>0.10</revnumber>
|
|
<date>2004-07-16</date>
|
|
<authorinitials>TS</authorinitials>
|
|
<revremark>
|
|
Added <?dbhtml..?> tags to control generated HTML
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|
filenames - should prevent broken links from google etc.
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|
Swapped order of "Forwarded Mail" and "User Settings".
|
|
Correction from Tony Finch on Bayesian filters;
|
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commented out check for Subject:, Date:, and Message-ID:
|
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headers per Johannes Berg; processing time subtracted
|
|
from SMTP delays per suggestion from Alan Flavell.
|
|
</revremark>
|
|
</revision>
|
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|
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<revision>
|
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<revnumber>0.09</revnumber>
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|
<date>2004-07-13</date>
|
|
<authorinitials>TS</authorinitials>
|
|
<revremark>
|
|
Elaborated on problems with envelope sender signatures
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and mailing list servers, and a scheme to make such
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signatures optional per host/domain for each user.
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Moved "Considerations" section out as a separate
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chapter; added subsections "Blocking Access to other
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SMTP Server", "User Settings" and "Forwarded Mail".
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Incorporated Matthew Byng-Maddick's comments on the
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|
mechanism used to generate these signatures, Chris
|
|
Edwards' comments on sender callout verification, and
|
|
Hadmut Danisch's comments on RMX++ and other topics.
|
|
Changed license terms (GPL instead of GFDL).
|
|
</revremark>
|
|
</revision>
|
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|
|
<revision>
|
|
<revnumber>0.08</revnumber>
|
|
<date>2004-07-09</date>
|
|
<authorinitials>TS</authorinitials>
|
|
<revremark>
|
|
Additional work on Exim implementation: Added section on
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|
per-user settings and data for SpamAssassin per
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|
suggestion from Tollef Fog Heen. Added SPF checks via
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|
Exiscan-ACL. Corrections from Sam Michaels.
|
|
</revremark>
|
|
</revision>
|
|
|
|
<revision>
|
|
<revnumber>0.07</revnumber>
|
|
<date>2004-07-08</date>
|
|
<authorinitials>TS</authorinitials>
|
|
<revremark>
|
|
Made corrections to the Exim Envelope Sender Signatures
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|
examples, and added support for users to "opt in" to
|
|
this feature, per suggestion from Christian Balzer.
|
|
</revremark>
|
|
</revision>
|
|
|
|
<revision>
|
|
<revnumber>0.06</revnumber>
|
|
<date>2004-07-08</date>
|
|
<authorinitials>TS</authorinitials>
|
|
<revremark>
|
|
Incorporated Exim/MySQL greylisting implementation and
|
|
various corrections from Johannes Berg. Moved "Sender
|
|
Authorization Schemes" up two levels to become a
|
|
top-level section in the Techniques chapter. Added
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greylisting for NULL empty envelope senders after DATA.
|
|
Added SpamAssassin configuration to match Exim examples.
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|
Incorporated corrections from Dominik Ruff, Mark
|
|
Valites, "Andrew" at Supernews.
|
|
</revremark>
|
|
</revision>
|
|
|
|
<revision>
|
|
<revnumber>0.05</revnumber>
|
|
<date>2004-07-07</date>
|
|
<authorinitials>TS</authorinitials>
|
|
<revremark>
|
|
Eliminated the (empty) Sendmail implementation for now,
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|
to move ahead with the final review process.
|
|
</revremark>
|
|
</revision>
|
|
|
|
<revision>
|
|
<revnumber>0.04</revnumber>
|
|
<date>2004-07-06</date>
|
|
<authorinitials>TS</authorinitials>
|
|
<revremark>
|
|
Reorganized layout a little: Combined "SMTP-Time
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|
Filtering", "Introduction to SMTP", and "Considerations"
|
|
into a single "Background" chapter. Split the previous
|
|
"Building ACLs" section in the Exim implementation into
|
|
top-level sections. Added alternate sender
|
|
authorization schemes to SPF: Microsoft Caller-ID for
|
|
E-Mail and RMX++. Incorporated comments from Ken
|
|
Raeburn.
|
|
</revremark>
|
|
</revision>
|
|
|
|
<revision>
|
|
<revnumber>0.03</revnumber>
|
|
<date>2004-07-02</date>
|
|
<authorinitials>TS</authorinitials>
|
|
<revremark>
|
|
Added discussion on Multiple Incoming Mail Exchangers;
|
|
minor corrections related to Sender Callout Verification.
|
|
</revremark>
|
|
</revision>
|
|
|
|
<revision>
|
|
<revnumber>0.02</revnumber>
|
|
<date>2004-06-30</date>
|
|
<authorinitials>TS</authorinitials>
|
|
<revremark>Added Exim implementation as an appendix</revremark>
|
|
</revision>
|
|
|
|
<revision>
|
|
<revnumber>0.01</revnumber>
|
|
<date>2004-06-16</date>
|
|
<authorinitials>TS</authorinitials>
|
|
<revremark>Initial draft.</revremark>
|
|
</revision>
|
|
</revhistory>
|
|
</para>
|
|
</section>
|
|
<!-- Give credit where credit is due...very important -->
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|
|
<section id="credits">
|
|
<?dbhtml filename="intro-credits.html"?>
|
|
<title>Credits</title>
|
|
|
|
<para>
|
|
A number of people have provided feedback, corrections, and
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|
contributions, as indicated in the <xref linkend="history"/>.
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|
Thank you!
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|
</para>
|
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|
|
<para>
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|
The following are <emphasis>some</emphasis> of the people and
|
|
groups that have provided tools and ideas to this document, in
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no particular order:
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</para>
|
|
|
|
<!-- Please scramble addresses; help prevent spam/email harvesting -->
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|
|
<itemizedlist>
|
|
<listitem>
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|
<para>
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Evan Harris <email>eharris (at) puremagic.com</email>, who
|
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conceived and wrote a white paper on <link
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|
linkend="greylisting">greylisting</link>.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
Axel Zinser <email>fifi (at) hiss.org</email>, who
|
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apparently conceived of
|
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<link linkend="smtpdelays">teergrubing</link>.
|
|
</para>
|
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</listitem>
|
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|
|
<listitem>
|
|
<para>
|
|
The developers of
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|
<ulink url="http://spf.pobox.com/">SPF</ulink>,
|
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<ulink url="http://www.danisch.de/work/security/antispam.html">RMX++</ulink>,
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and other
|
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<xref linkend="senderauth"/>.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
The creators and maintainers of distributed, collaborative
|
|
junk mail signature repositories, such as
|
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<ulink url="http://rhyolite.com/anti-spam/dcc/">DCC</ulink>,
|
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<ulink url="http://razor.sf.net/">Razor</ulink>, and
|
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<ulink url="http://pyzor.sf.net/">Pyzor</ulink>.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
The creators and maintainers of various DNS blocklists and
|
|
whitelists, such as
|
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<ulink url="http://www.spamcop.net/">SpamCop</ulink>,
|
|
<ulink url="http://www.spamhaus.org/">SpamHaus</ulink>,
|
|
<ulink url="http://www.sorbs.net/">SORBS</ulink>,
|
|
<ulink url="http://cbl.abuseat.org/">CBL</ulink>, and
|
|
<ulink url="http://moensted.dk/spam/">many others</ulink>.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
The
|
|
<ulink url="http://www.spamassassin.org/full/3.0.x/dist/CREDITS">developers</ulink>
|
|
of
|
|
<ulink url="http://www.spamassassin.org/">SpamAssassin</ulink>,
|
|
who have taken giant leaps forward in developing and
|
|
integrating various spam filtering techniques into a
|
|
sophisticated heuristics-based tool.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
Tim Jackson <email>tim (at) timj.co.uk</email> collated
|
|
and maintains a list of
|
|
<link linkend="bogusviruswarning">bogus virus warnings</link>
|
|
for use with SpamAssassin.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
A lot of smart people who developed the excellent <link
|
|
linkend="exim">Exim</link> MTA, including: Philip
|
|
Hazel <email>ph10 (at) cus.cam.ac.uk</email>, the
|
|
maintainer; Tom Kistner <email>tom (at)
|
|
duncanthrax.net</email>, who wrote the Exiscan-ACL patch
|
|
for SMTP-time content checks; Andreas Metzler
|
|
<email>ametzler (at) debian.org</email>, who did a really
|
|
good job of building the Exim 4 Debian packages.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
Many, many others who contributed ideas, software, and
|
|
other techniques to counter the spam epidemic.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
You, for reading this document and your interest in
|
|
reclaiming e-mail as a useful communication tool
|
|
</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
</section>
|
|
<!-- Feedback -->
|
|
|
|
<section id="feedback">
|
|
<?dbhtml filename="intro-feedback.html"?>
|
|
<title>Feedback</title>
|
|
|
|
<para>
|
|
I would love to hear of your experiences with the techniques
|
|
outlined in this document, and of any other comments,
|
|
questions, suggestions, and/or contributions you may have.
|
|
Please send me an e-mail at: <email>tor@slett.net</email>.
|
|
</para>
|
|
|
|
<para>
|
|
If you are able to provide implementations for other <xref
|
|
linkend="mta"/>s, such as Sendmail or Postfix, please let me
|
|
know.
|
|
</para>
|
|
</section>
|
|
<!-- Translations -->
|
|
|
|
<section id="translations">
|
|
<?dbhtml filename="intro-translations.html"?>
|
|
<title>Translations</title>
|
|
|
|
<para>
|
|
No translations exist yet. If you would like to create one,
|
|
please let me know.
|
|
</para>
|
|
</section>
|
|
|
|
<section id="copyright">
|
|
<?dbhtml filename="intro-copyright.html"?>
|
|
<title>Copyright information</title>
|
|
|
|
<para>
|
|
Copyright © 2004 Tor Slettnes.
|
|
</para>
|
|
|
|
<para>
|
|
This document is free software; you can redistribute it and/or
|
|
modify it under the terms of the GNU General Public License as
|
|
published by the Free Software Foundation; either version 2 of
|
|
the License, or (at your option) any later version.
|
|
</para>
|
|
|
|
<para>
|
|
This document is distributed in the hope that it will be
|
|
useful, but WITHOUT ANY WARRANTY; without even the implied
|
|
warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
|
|
PURPOSE. See the GNU General Public License for more details.
|
|
A copy of the license is included in <xref linkend="gpl"/>.
|
|
</para>
|
|
|
|
<para>
|
|
Read <ulink url="http://www.fsf.org/gnu/manifesto.html">The
|
|
GNU Manifesto </ulink> if you want to know why this license
|
|
was chosen for this book.
|
|
</para>
|
|
|
|
<para>
|
|
The logos, trademarks and symbols used in this book are the
|
|
properties of their respective owners.
|
|
</para>
|
|
</section>
|
|
|
|
<section id="prerequisites">
|
|
<?dbhtml filename="intro-prerequisites.html"?>
|
|
<title>What do you need?</title>
|
|
|
|
<para>
|
|
The techniques described in this document predicate system
|
|
access to the inbound <xref linkend="mx"/>(s) for the internet
|
|
domain where you receive e-mail. Essentially, you need to be
|
|
able to install software and/or modify the configuration files
|
|
for the <xref linkend="mta"/> on that system.
|
|
</para>
|
|
|
|
<para>
|
|
Although the discussions in this document are conceptual in
|
|
nature and can be incorporated into a number of different
|
|
MTAs, a sample Exim 4 implementation is provided. This
|
|
implementation, in turn, incorporates other software tools,
|
|
such as <ulink
|
|
url="http://www.spamassassin.org/">SpamAssassin</ulink>.
|
|
See <xref linkend="exim"/> for details.
|
|
</para>
|
|
</section>
|
|
|
|
<section id="conventions">
|
|
<?dbhtml filename="intro-conventions.html"?>
|
|
<title>Conventions used in this document</title>
|
|
|
|
<para>
|
|
The following typographic and usage conventions occur in this text:
|
|
</para>
|
|
|
|
<table id="conventiontable" frame="all">
|
|
<title>Typographic and usage conventions</title>
|
|
|
|
<tgroup cols="2" align="left" colsep="1" rowsep="1">
|
|
|
|
<thead>
|
|
<row>
|
|
<entry>Text type</entry>
|
|
<entry>Meaning</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry><quote>Quoted text</quote></entry>
|
|
<entry>Quotes from people, quoted computer output.</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><screen>terminal view</screen></entry>
|
|
<entry>
|
|
Literal computer input and output captured from
|
|
the terminal, usually rendered with a light grey
|
|
background.
|
|
</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><command>command</command></entry>
|
|
<entry>
|
|
Name of a command that can be entered on the command
|
|
line.
|
|
</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><varname>VARIABLE</varname></entry>
|
|
<entry>
|
|
Name of a variable or pointer to content of a
|
|
variable, as in <varname>$VARNAME</varname>.
|
|
</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><option>option</option></entry>
|
|
<entry>
|
|
Option to a command, as in <quote>the
|
|
<option>-a</option> option to the
|
|
<command>ls</command> command</quote>.
|
|
</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><parameter>argument</parameter></entry>
|
|
<entry>
|
|
Argument to a command, as in
|
|
<quote>read <command>man
|
|
<parameter>ls</parameter></command>
|
|
</quote>.
|
|
</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry>
|
|
<cmdsynopsis>
|
|
<command>command
|
|
<option>options</option>
|
|
<parameter>arguments</parameter>
|
|
</command>
|
|
</cmdsynopsis>
|
|
</entry>
|
|
<entry>
|
|
Command synopsis or general usage, on a separated
|
|
line.
|
|
</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><filename>filename</filename></entry>
|
|
<entry>
|
|
Name of a file or directory, for example <quote>Change
|
|
to the <filename>/usr/bin</filename>
|
|
directory.</quote>
|
|
</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><keycap>Key</keycap></entry>
|
|
<entry>
|
|
Keys to hit on the keyboard, such as <quote>type
|
|
<keycap>Q</keycap> to quit</quote>.
|
|
</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><guibutton>Button</guibutton></entry>
|
|
<entry>
|
|
Graphical button to click, like the
|
|
<guibutton>OK</guibutton> button.
|
|
</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry>
|
|
<menuchoice>
|
|
<guimenu>Menu</guimenu>
|
|
<guimenuitem>Choice</guimenuitem>
|
|
</menuchoice>
|
|
</entry>
|
|
<entry>
|
|
Choice to select from a graphical menu, for instance:
|
|
<quote>Select
|
|
<menuchoice><guimenu>Help</guimenu><guimenuitem>About
|
|
Mozilla</guimenuitem> </menuchoice> in your
|
|
browser.</quote></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry>
|
|
<emphasis>Terminology</emphasis></entry>
|
|
<entry>
|
|
Important term or concept:
|
|
<quote>The Linux <emphasis>kernel</emphasis>
|
|
is the heart of the system.</quote>
|
|
</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry>
|
|
See <xref linkend="glossary" />
|
|
</entry>
|
|
<entry>
|
|
link to related subject within this guide.
|
|
</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry>
|
|
<ulink
|
|
url="http://slett.net/gallery/2003-05/IMG_1655">The author</ulink>
|
|
</entry>
|
|
<entry>Clickable link to an external web resource.</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
</section>
|
|
|
|
<section id="organization">
|
|
<?dbhtml filename="intro-organization.html"?>
|
|
<title>Organization of this document</title>
|
|
|
|
<para>
|
|
This document is organized into the following chapters:
|
|
</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><xref linkend="background"/></term>
|
|
<listitem>
|
|
<para>
|
|
General introduction to SMTP time filtering, and to SMTP.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><xref linkend="techniques"/></term>
|
|
<listitem>
|
|
<para>
|
|
Various ways to block junk mail in an SMTP transaction.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><xref linkend="considerations"/></term>
|
|
<listitem>
|
|
<para>
|
|
Issues that pertain to transaction time filtering.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><xref linkend="qanda"/></term>
|
|
<listitem>
|
|
<para>
|
|
My attempt at anticipating your questions, and then
|
|
answering them.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
|
|
|
|
<para>
|
|
A sample Exim implementation is provided in <xref
|
|
linkend="exim"/>.
|
|
</para>
|
|
</section>
|
|
</preface>
|
|
|
|
<toc></toc>
|
|
|
|
&background;
|
|
&techniques;
|
|
&consider;
|
|
&qanda;
|
|
&exim;
|
|
&glossary;
|
|
&gpl;
|
|
</book>
|