1<HTML> 2<HEAD> 3<TITLE>Filtering Mail with Sendmail</TITLE> 4</HEAD> 5<BODY> 6<!-- 7$Id: index.html,v 1.14 2013-11-22 20:51:39 ca Exp $ 8--> 9 10<H1>Filtering Mail with Sendmail</H1> 11 12<!-- 13<P><B>Disclaimer</B>: 14This preliminary API description is provided for review only. This 15specification may change based on feedback from reviewers, and does 16not bind Sendmail to offer this functionality in any release. 17--> 18 19<H2>Introduction</H2> 20 21<P> 22Sendmail's Content Management API (milter) provides third-party 23programs to access mail messages as they are being processed by the 24Mail Transfer Agent (MTA), allowing them to examine and modify message 25content and meta-information. Filtering policies implemented by 26Milter-conformant filters may then be centrally configured and 27composed in an end-user's MTA configuration file. 28 29<P> 30Possible uses for filters include spam rejection, virus 31filtering, and content control. In general, Milter seeks to address 32site-wide filtering concerns in a scalable way. Individual users' mail 33filtering needs (e.g. sorting messages by subject) are left to 34client-level programs such as <A href="http://www.procmail.org">Procmail</A>. 35 36<P> 37This document is a technical introduction intended for those 38interested in developing Milter filters. It includes: 39<UL> 40<LI>A description of Milter's design goals. 41 42<LI>An explanation of Milter application architecture, including 43interactions between the support library and user code, and between 44filters and the MTA. 45 46<LI>A specification of the C application programming interface. 47<LI>An example of a simple Milter filter. 48</UL> 49 50<H2>Contents</H2> 51 52<UL> 53<LI><A href="design.html">Architecture</A> 54<UL> 55 <LI>Design Goals 56 <LI>Implementing Filtering Policies 57 <LI>MTA - Filter communication 58</UL> 59<LI><A href="overview.html">Technical Overview</A> 60<UL> 61 <LI>Initialization 62 <LI>Control flow 63 <LI>Multithreading 64 <LI>Resource Management 65 <LI>Signal Handling 66</UL> 67<LI><A href="api.html">API Documentation</A> 68<UL> 69 <LI>Library Control Functions 70 <LI>Data Access Functions 71 <LI>Message Modification Functions 72 <LI>Callbacks 73</UL> 74<LI><A href="installation.html">Installation and Configuration</A> 75<UL> 76 <LI>Compiling and Installing Your Filter 77 <LI>Configuring Sendmail 78</UL> 79<LI><A href="sample.html">A Sample Filter</A> 80<!-- <LI><A href="other.html">Other Sources of Information</A> --> 81</UL> 82 83<HR size="1"> 84<FONT size="-1"> 85Copyright (c) 2000, 2001, 2003 Proofpoint, Inc. and its suppliers. 86All rights reserved. 87<BR> 88By using this file, you agree to the terms and conditions set 89forth in the LICENSE. 90</FONT> 91</BODY> 92</HTML> 93