<html> <head> <title>Filtering Mail with Sendmail</title> </head> <body> <!-- $Id: index.html,v 1.10 2001/06/01 00:05:03 ca Exp $ --> <h1>Filtering Mail with Sendmail</h1> <!-- <P><b>Disclaimer</b>: This preliminary API description is provided for review only. This specification may change based on feedback from reviewers, and does not bind Sendmail to offer this functionality in any release. --> <h2>Introduction</h2> <P> Sendmail's Content Management API (milter) provides third-party programs to access mail messages as they are being processed by the Mail Transfer Agent (MTA), allowing them to examine and modify message content and meta-information. Filtering policies implemented by Milter-conformant filters may then be centrally configured and composed in an end-user's MTA configuration file. <p> Possible uses for filters include spam rejection, virus filtering, and content control. In general, Milter seeks to address site-wide filtering concerns in a scalable way. Individual users' mail filtering needs (e.g. sorting messages by subject) are left to client-level programs such as <a href="http://www.procmail.org">Procmail</a>. <P> This document is a technical introduction intended for those interested in developing Milter filters. It includes: <ul> <li>A description of Milter's design goals. <li>An explanation of Milter application architecture, including interactions between the support library and user code, and between filters and the MTA. <li>A specification of the C application programming interface. <li>An example of a simple Milter filter. </ul> <h2>Contents</h2> <ul> <li><a href="design.html">Architecture</a> <ul> <li>Design Goals <li>Implementing Filtering Policies <li>MTA - Filter communication </ul> <li><a href="overview.html">Technical Overview</a> <ul> <li>Initialization <li>Control flow <li>Multithreading <li>Resource Management <li>Signal Handling </ul> <li><a href="api.html">API Documentation</a> <ul> <li>Library Control Functions <li>Data Access Functions <li>Message Modification Functions <li>Callbacks </ul> <li><a href="installation.html">Installation and Configuration</a> <ul> <li>Compiling and Installing Your Filter <li>Configuring Sendmail </ul> <li><a href="sample.html">A Sample Filter</a> <!-- <li><a href="other.html">Other Sources of Information</a> --> </ul> <hr size="1"> <font size="-1"> Copyright (c) 2000, 2001 Sendmail, Inc. and its suppliers. All rights reserved. <br> By using this file, you agree to the terms and conditions set forth in the <a href="LICENSE.txt">LICENSE</a>. </font> </body> </html>