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3<TITLE>Filtering Mail with Sendmail</TITLE>
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10<H1>Filtering Mail with Sendmail</H1>
11
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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
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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
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