<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML ><HEAD ><TITLE >Purpose of this Document</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.7"><LINK REL="HOME" TITLE="Spam Filtering for Mail Exchangers" HREF="index.html"><LINK REL="UP" TITLE="Introduction" HREF="introduction.html"><LINK REL="PREVIOUS" TITLE="Introduction" HREF="introduction.html"><LINK REL="NEXT" TITLE="Audience" HREF="intro-audience.html"></HEAD ><BODY CLASS="section" BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#840084" ALINK="#0000FF" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="3" ALIGN="center" >Spam Filtering for Mail Exchangers: </TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="introduction.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" >Introduction</TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="intro-audience.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="section" ><H1 CLASS="section" ><A NAME="purpose" ></A >1. Purpose of this Document</H1 ><P > This document discusses various highly effective and low impact ways to weed out spam and malware during incoming SMTP transactions in a mail exchanger (MX host), with an added emphasis on eliminating so-called <A HREF="gloss.html#colspam" ><I CLASS="glossterm" >Collateral Spam</I ></A >. </P ><P > The discussions are conceptual in nature, but a sample implementation is provided using the Exim MTA and other specific software tools. Miscellaneous other bigotry is expressed throughout. </P ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="introduction.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="intro-audience.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >Introduction</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="introduction.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >Audience</TD ></TR ></TABLE ></DIV ></BODY ></HTML >