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3168515Sgshapiro<TITLE>Filtering Mail with Sendmail</TITLE>
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1090792Sgshapiro<H1>Filtering Mail with Sendmail</H1>
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12168515Sgshapiro<!--
1390792Sgshapiro<P><B>Disclaimer</B>: 
1490792SgshapiroThis preliminary API description is provided for review only.  This
15168515Sgshapirospecification may change based on feedback from reviewers, and does
1690792Sgshapironot bind Sendmail to offer this functionality in any release.
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1890792Sgshapiro
19168515Sgshapiro<H2>Introduction</H2>
2090792Sgshapiro
2190792Sgshapiro<P>
22168515SgshapiroSendmail's Content Management API (milter) provides third-party
23168515Sgshapiroprograms to access mail messages as they are being processed by the
24168515SgshapiroMail Transfer Agent (MTA), allowing them to examine and modify message
25168515Sgshapirocontent and meta-information.  Filtering policies implemented by
26168515SgshapiroMilter-conformant filters may then be centrally configured and
27168515Sgshapirocomposed in an end-user's MTA configuration file.
28168515Sgshapiro
29168515Sgshapiro<P>
30168515SgshapiroPossible uses for filters include spam rejection, virus
31168515Sgshapirofiltering, and content control.  In general, Milter seeks to address
32168515Sgshapirosite-wide filtering concerns in a scalable way.  Individual users' mail
3390792Sgshapirofiltering needs (e.g. sorting messages by subject) are left to
3490792Sgshapiroclient-level programs such as <A href="http://www.procmail.org">Procmail</A>.
35168515Sgshapiro
36168515Sgshapiro<P>
37168515SgshapiroThis document is a technical introduction intended for those
38168515Sgshapirointerested in developing Milter filters.  It includes:
39168515Sgshapiro<UL>
40168515Sgshapiro<LI>A description of Milter's design goals.
41168515Sgshapiro
42168515Sgshapiro<LI>An explanation of Milter application architecture, including
4390792Sgshapirointeractions between the support library and user code, and between
4490792Sgshapirofilters and the MTA.
45168515Sgshapiro
46168515Sgshapiro<LI>A specification of the C application programming interface.
47168515Sgshapiro<LI>An example of a simple Milter filter.
48168515Sgshapiro</UL>
49168515Sgshapiro
50168515Sgshapiro<H2>Contents</H2>
51168515Sgshapiro
5290792Sgshapiro<UL>
53168515Sgshapiro<LI><A href="design.html">Architecture</A>
54168515Sgshapiro<UL>
55261363Sgshapiro    <LI>Design Goals
5690792Sgshapiro    <LI>Implementing Filtering Policies
57168515Sgshapiro    <LI>MTA - Filter communication
5890792Sgshapiro</UL>
59112810Sgshapiro<LI><A href="overview.html">Technical Overview</A>
60168515Sgshapiro<UL>
61168515Sgshapiro    <LI>Initialization
62168515Sgshapiro    <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
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