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<A NAME="CHILD_LINKS"><STRONG>Subsections</STRONG></A>

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<LI><A NAME="tex2html2377"
  HREF="#SECTION003310000000000000000">30.1 Introduction</A>
<UL>
<LI><A NAME="tex2html2378"
  HREF="#SECTION003311000000000000000">30.1.1 How mail works</A>
<LI><A NAME="tex2html2379"
  HREF="#SECTION003312000000000000000">30.1.2 Configuring a POP/IMAP server</A>
<LI><A NAME="tex2html2380"
  HREF="#SECTION003313000000000000000">30.1.3 Why <TT>
<FONT COLOR="#0000ff">exim</FONT></TT>?</A>
</UL>
<LI><A NAME="tex2html2381"
  HREF="#SECTION003320000000000000000">30.2 <TT>
<FONT COLOR="#0000ff">exim</FONT></TT> Package Contents</A>
<LI><A NAME="tex2html2382"
  HREF="#SECTION003330000000000000000">30.3 <TT>
<FONT COLOR="#0000ff">exim</FONT></TT> Configuration File</A>
<UL>
<LI><A NAME="tex2html2383"
  HREF="#SECTION003331000000000000000">30.3.1 Global settings</A>
<LI><A NAME="tex2html2384"
  HREF="#SECTION003332000000000000000">30.3.2 Transports</A>
<LI><A NAME="tex2html2385"
  HREF="#SECTION003333000000000000000">30.3.3 Directors</A>
<LI><A NAME="tex2html2386"
  HREF="#SECTION003334000000000000000">30.3.4 Routers</A>
</UL>
<LI><A NAME="tex2html2387"
  HREF="#SECTION003340000000000000000">30.4 Full-blown Mail server</A>
<LI><A NAME="tex2html2388"
  HREF="#SECTION003350000000000000000">30.5 Shell Commands for <TT>
<FONT COLOR="#0000ff">exim</FONT></TT> Administration</A>
<LI><A NAME="tex2html2389"
  HREF="#SECTION003360000000000000000">30.6 The Queue</A>
<LI><A NAME="tex2html2390"
  HREF="#SECTION003370000000000000000">30.7 <TT>
<FONT COLOR="#0000ff">/etc/aliases</FONT></TT> for Equivalent Addresses</A>
<LI><A NAME="tex2html2391"
  HREF="#SECTION003380000000000000000">30.8 Real-Time Blocking List -- Combating Spam</A>
<UL>
<LI><A NAME="tex2html2392"
  HREF="#SECTION003381000000000000000">30.8.1 What is <I>spam</I>?</A>
<LI><A NAME="tex2html2393"
  HREF="#SECTION003382000000000000000">30.8.2 Basic spam prevention</A>
<LI><A NAME="tex2html2394"
  HREF="#SECTION003383000000000000000">30.8.3 Real-time blocking list</A>
<LI><A NAME="tex2html2395"
  HREF="#SECTION003384000000000000000">30.8.4 Mail administrator and user responsibilities</A>
</UL>
<LI><A NAME="tex2html2396"
  HREF="#SECTION003390000000000000000">30.9 Sendmail</A>
</UL>
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<HR>

<H1><A NAME="SECTION003300000000000000000">
30. <TT>
<FONT COLOR="#0000ff">exim</FONT></TT> and <TT>
<FONT COLOR="#0000ff">sendmail</FONT></TT></A>
</H1>

<P>
<A NAME="chap:eximsendmail"></A>
<P>
This chapter effectively explains how to get L<SMALL>INUX</SMALL> up and
running as a mail server. I have also included discussion on
the process of mail delivery right through to retrieval of
mail using POP and IMAP.

<P>

<H1><A NAME="SECTION003310000000000000000">
30.1 Introduction</A>
</H1>

<P>
<TT>
<FONT COLOR="#0000ff">exim</FONT></TT> and
<TT>
<FONT COLOR="#0000ff">sendmail</FONT></TT> are <I>MTA</I>s (<I>mail
transfer agents</I>). An MTA is just a daemon process that listens on
port 25 for incoming mail connections, spools <FONT COLOR="#ffa500">[See page
<A HREF="node24.html#page:spoolfile"><IMG  ALIGN="BOTTOM" BORDER="1" ALT="[*]" SRC="crossref.png"></A> about spooling in general.]</FONT> that mail in a
<I>queue</I> (for <TT>
<FONT COLOR="#0000ff">exim</FONT></TT>, the
<TT>
<FONT COLOR="#0000ff">/var/spool/exim/input/</FONT></TT> directory,
for <TT>
<FONT COLOR="#0000ff">sendmail</FONT></TT>, the <TT>
<FONT COLOR="#0000ff">/var/spool/mqueue/</FONT></TT>
directory),
then resends that mail to some other MTA or
delivers it locally to some user's mailbox. In other
words, the MTA is the very package that handles all mail spooling,
routing, and delivery.
We saw in Section <A HREF="node13.html#sec:sendamail">10.2</A> how to
manually connect to an MTA with <TT>
<FONT COLOR="#0000ff">telnet</FONT></TT>.
In that example, <TT>
<FONT COLOR="#0000ff">sendmail</FONT></TT>
version 8.9.3 was the MTA running on machine <TT>
<FONT COLOR="#0000ff">mail.cranzgot.co.za</FONT></TT>.

<P>
<TT>
<FONT COLOR="#0000ff">sendmail</FONT></TT> is the original and popular U<SMALL>NIX</SMALL> MTA. It is probably
necessary to learn how to configure it because so many organizations
standardize on it. However, because <TT>
<FONT COLOR="#0000ff">exim</FONT></TT> is so easy to configure, it is
worthwhile replacing <TT>
<FONT COLOR="#0000ff">sendmail</FONT></TT> wherever you see it--there
are at least three MTAs that are preferable to <TT>
<FONT COLOR="#0000ff">sendmail</FONT></TT>.
I explain the minimum of what you need to know about
<TT>
<FONT COLOR="#0000ff">sendmail</FONT></TT> later on and explain <TT>
<FONT COLOR="#0000ff">exim</FONT></TT> in detail.

<P>

<H2><A NAME="SECTION003311000000000000000">
30.1.1 How mail works</A>
</H2>

<P>
Before we get into MTA configuration, a background in mail delivery and
indexii<TT>
<FONT COLOR="#0000ff">MX</FONT></TT> recordDNSMX record
handling is necessary. The sequence of events whereby a mail message (sent
by a typical interactive mail client) ends up on a
distant user's personal workstation is as follows:

<OL>
<LI>A user configures his mail client (Outlook Express, Netscape, etc.)
to use a particular <I>SMTP host</I> (for
<I>outgoing mail</I>, also called the
<I>SMTP gateway</I>) and
<I>POP host</I> (or <I>IMAP host</I>)
for <I>incoming mail</I>.
</LI>
<LI>The user composes a message to, say,
<TT>
<FONT COLOR="#0000ff">rrabbit@toonland.net</FONT></TT> and then clicks on ``Send.''
</LI>
<LI>The mail client initiates an outgoing TCP
connection to port 25 of the SMTP host.
An MTA running on the SMTP host and listening on port 25 services the request.
The mail client uses the SMTP protocol exactly as in Section <A HREF="node13.html#sec:sendamail">10.2</A>.
It fills in <TT>
<FONT COLOR="#0000ff">rrabbit@toonland.net</FONT></TT> as the recipient address
and transfers a properly composed header (hopefully)
and message body to the
MTA. The mail client then terminates the connection and reports any errors.
</LI>
<LI>The MTA queues the message as a spool file, periodically considering
whether to process the message further according to a retry schedule.
</LI>
<LI>Should the retry schedule permit, the MTA considers the
recipient address <TT>
<FONT COLOR="#0000ff">rrabbit@toonland.net</FONT></TT>. It strips out the
<I>domain part</I> of the email address--that is, everything after
the <TT>
<FONT COLOR="#0000ff">@</FONT></TT>. It then performs a DNS
<I>MX query</I> (or <I>MX lookup</I>indexii<TT>
<FONT COLOR="#0000ff">MX</FONT></TT> recordDNS) for the
domain <TT>
<FONT COLOR="#0000ff">toonland.net</FONT></TT>. DNS resolution for <TT>
<FONT COLOR="#0000ff">toonland.net</FONT></TT>
follows the procedure listed in Section <A HREF="node30.html#sec:nameresprocess">27.2.2</A>.
In short, this means (approximately) that it looks for the name
server that is authoritative for the domain <TT>
<FONT COLOR="#0000ff">toonland.net</FONT></TT>. It
queries that name server for the MX record of the domain <TT>
<FONT COLOR="#0000ff">toonland.net</FONT></TT>.
The name server returns a host name, say, <TT>
<FONT COLOR="#0000ff">mail.toonland.net</FONT></TT>
with corresponding IP address, say,
<TT>
<FONT COLOR="#0000ff">197.21.135.82</FONT></TT>. <FONT COLOR="#ffa500">[Section <A HREF="node30.html#sec:nsmxrecords">27.7.1</A> shows you
how you can manually lookup the MX record. Chapter <A HREF="node43.html#chap:name">40</A> shows
you how to set up your name server to return such an MX record.]</FONT>
</LI>
<LI>The MTA makes an SMTP connection to port 25 of <TT>
<FONT COLOR="#0000ff">197.21.135.82</FONT></TT>.
Another MTA running on <TT>
<FONT COLOR="#0000ff">mail.toonland.net</FONT></TT> services the request.
A recipient address, message header, and message body are transferred
using the SMTP protocol. The MTA then terminates the connection.
</LI>
<LI>The MTA running on <TT>
<FONT COLOR="#0000ff">mail.toonland.net</FONT></TT> considers the recipient
address <TT>
<FONT COLOR="#0000ff">rrabbit@toonland.net</FONT></TT>. It recognizes <TT>
<FONT COLOR="#0000ff">toonland.net</FONT></TT>
as a domain for which it hosts mail (that is, a <I>local domain</I>).
It recognizes <TT>
<FONT COLOR="#0000ff">rrabbit</FONT></TT> as a user name within its own
<TT>
<FONT COLOR="#0000ff">/etc/passwd</FONT></TT> file.
</LI>
<LI>The MTA running on <TT>
<FONT COLOR="#0000ff">mail.toonland.net</FONT></TT> appends the message
to the user's personal mailbox file, say, <TT>
<FONT COLOR="#0000ff">/var/spool/mail/rrabbit</FONT></TT>
or <TT>
<FONT COLOR="#0000ff">/home/rrabbit/Maildir/</FONT></TT>.
<I>The delivery is now complete. How the email gets from the mailbox
on <TT>
<FONT COLOR="#0000ff">mail.toonland.net</FONT></TT> to Mr Rabbit's personal workstation is
<I>not</I> the responsibility of the MTA and does <I>not</I> happen
through SMTP.</I>
</LI>
<LI>Mr Rabbit would have configured his mail client (running on his personal
workstation) to use a POP/IMAP host <TT>
<FONT COLOR="#0000ff">mail.toonland.net</FONT></TT> for incoming
mail. <TT>
<FONT COLOR="#0000ff">mail.toonland.net</FONT></TT> runs a POP or IMAP service on
port 110 or 143, respectively.
</LI>
<LI>Mr Rabbit's mail client makes a TCP connection to port 110 (or 143)
and communicates using the POP or IMAP protocol. The POP or IMAP service
is responsible for feeding the message to the mail client and deleting
it from the mailbox file.
</LI>
<LI>Mr Rabbit's mail client stores the message on his
workstation using its own methods and displays the message
as a ``new'' message.
</LI>
</OL>

<P>

<H2><A NAME="SECTION003312000000000000000">
30.1.2 Configuring a POP/IMAP server</A>
</H2>

<P>
POP and IMAP are invoked by <TT>
<FONT COLOR="#0000ff">inetd</FONT></TT> or
<TT>
<FONT COLOR="#0000ff">xinetd</FONT></TT>--see Chapter <A HREF="node32.html#chap:xinetd">29</A>.
Except for limiting the range of clients that are allowed
to connect (for 
security reasons), no configuration is required.
Client connections authenticate themselves using the
normal U<SMALL>NIX</SMALL> login name and password. There are
specialized POP and IMAP packages for supporting
different mailbox types (like Maildir).

<P>

<H2><A NAME="SECTION003313000000000000000">
30.1.3 Why <TT>
<FONT COLOR="#0000ff">exim</FONT></TT>?</A>
</H2>

<P>
The <TT>
<FONT COLOR="#0000ff">exim</FONT></TT> <EM>home page</EM> <I>&lt;<TT><A NAME="tex2html43"
  HREF="http://www.exim.org/">http://www.exim.org/</A></TT>&gt;</I> gives
you a full rundown. Here I will just say that <TT>
<FONT COLOR="#0000ff">exim</FONT></TT> is the
simplest MTA to configure. Moreover, its configuration file works the same
way you imagine mail to work. It's really easy to customize the <TT>
<FONT COLOR="#0000ff">exim</FONT></TT>
configuration to do some really weird things. The whole package fits
together cleanly, logically, and intuitively. This is in contrast to
<TT>
<FONT COLOR="#0000ff">sendmail</FONT></TT>'s <TT>
<FONT COLOR="#0000ff">sendmail.cf</FONT></TT>
file, which is widely considered
to be extremely cryptic and impractical. <TT>
<FONT COLOR="#0000ff">exim</FONT></TT> also seems to
have been written with proper security considerations, although
many people argue that <TT>
<FONT COLOR="#0000ff">postfix</FONT></TT> and
<TT>
<FONT COLOR="#0000ff">qmail</FONT></TT> are the last word in
secure mail.

<P>

<H1><A NAME="SECTION003320000000000000000">
30.2 <TT>
<FONT COLOR="#0000ff">exim</FONT></TT> Package Contents</A>
</H1>

<P>
You can get <TT>
<FONT COLOR="#0000ff">exim</FONT></TT> as a <TT>
<FONT COLOR="#0000ff">.rpm</FONT></TT> or <TT>
<FONT COLOR="#0000ff">.deb</FONT></TT> file. After
installation, the file
<TT>
<FONT COLOR="#0000ff">/usr/share/doc/exim-</FONT></TT><I>?</I><TT>
<FONT COLOR="#0000ff">.</FONT></TT><I>??</I><TT>
<FONT COLOR="#0000ff">/doc/spec.txt</FONT></TT> <FONT COLOR="#ffa500">[or <TT>
<FONT COLOR="#0000ff">/usr/doc/</FONT></TT>]</FONT>contains the complete <TT>
<FONT COLOR="#0000ff">exim</FONT></TT> documentation; there is also an HTML version
on the <TT>
<FONT COLOR="#0000ff">exim</FONT></TT> web page, whereas the man page contains only command-line information.
<TT>
<FONT COLOR="#0000ff">exim</FONT></TT> is a drop-in replacement for <TT>
<FONT COLOR="#0000ff">sendmail</FONT></TT>, meaning that for every critical
<TT>
<FONT COLOR="#0000ff">sendmail</FONT></TT> command, there is an <TT>
<FONT COLOR="#0000ff">exim</FONT></TT> command of the same name
that takes the same options, so that needy scripts won't know the
difference. These are:

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>/etc/aliases</code><br>
<code>/usr/bin/mailq</code><br>
<code>/usr/bin/newaliases</code><br>
<code>/usr/bin/rmail</code><br>
<code>/usr/lib/sendmail</code><br>
<code>/usr/sbin/sendmail</code><br>
</FONT></TD></TR></TABLE><P>
Finally, there is the <TT>
<FONT COLOR="#0000ff">exim</FONT></TT> binary itself,
<TT>
<FONT COLOR="#0000ff">/usr/sbin/exim</FONT></TT>, and configuration file
<TT>
<FONT COLOR="#0000ff">/etc/exim/config</FONT></TT>,
<TT>
<FONT COLOR="#0000ff">/etc/exim.conf</FONT></TT>, or
<TT>
<FONT COLOR="#0000ff">/etc/exim/exim.conf</FONT></TT>,
depending on your L<SMALL>INUX</SMALL> distribution.
Then there are the usual start/stop scripts,
<TT>
<FONT COLOR="#0000ff">/etc/init.d/exim</FONT></TT>. <FONT COLOR="#ffa500">[or <TT>
<FONT COLOR="#0000ff">/etc/rc.d/init.d/exim</FONT></TT>]</FONT>
<P>

<H1><A NAME="SECTION003330000000000000000">
30.3 <TT>
<FONT COLOR="#0000ff">exim</FONT></TT> Configuration File</A>
</H1>

<P>
As a preliminary example, here we create a simple spooling mail server
for a personal workstation, <TT>
<FONT COLOR="#0000ff">cericon.cranzgot.co.za</FONT></TT>.

<P>
Client applications (especially non-U<SMALL>NIX</SMALL> ones) are usually
configured to connect to an MTA running on a remote machine, however,
using a remote SMTP host can be irritating if the host or network
go down. Running <TT>
<FONT COLOR="#0000ff">exim</FONT></TT> on the local workstation enables all
applications to use <TT>
<FONT COLOR="#0000ff">localhost</FONT></TT> as their SMTP gateway:
that is, <TT>
<FONT COLOR="#0000ff">exim</FONT></TT> takes care of queuing
and periodic retries.

<P>
Here is the configuration. The difference between this
and a full-blown mail server is actually very slight.

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>10</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>15</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>20</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>25</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>30</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>35</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>40</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>45</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>50</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>####################&nbsp;MAIN&nbsp;CONFIGURATION&nbsp;SETTINGS&nbsp;#####################</code><br>
<code>log_subject</code><br>
<code>errors_address&nbsp;=&nbsp;postmaster</code><br>
<code>freeze_tell_mailmaster&nbsp;=&nbsp;yes</code><br>
<code>queue_list_requires_admin&nbsp;=&nbsp;false</code><br>
<code>prod_requires_admin&nbsp;=&nbsp;false</code><br>
<code>trusted_users&nbsp;=&nbsp;psheer</code><br>
<code>local_domains&nbsp;=&nbsp;localhost&nbsp;:&nbsp;${primary_hostname}</code><br>
<code>never_users&nbsp;=&nbsp;root</code><br>
<code>#&nbsp;relay_domains&nbsp;=&nbsp;my.equivalent.domains&nbsp;:&nbsp;more.equivalent.domains</code><br>
<code>host_accept_relay&nbsp;=&nbsp;localhost&nbsp;:&nbsp;*.cranzgot.co.za&nbsp;:&nbsp;192.168.0.0/16</code><br>
<code>exim_user&nbsp;=&nbsp;mail</code><br>
<code>exim_group&nbsp;=&nbsp;mail</code><br>
<code>end</code><br>
<code>&nbsp;</code><br>
<code>######################&nbsp;TRANSPORTS&nbsp;CONFIGURATION&nbsp;######################</code><br>
<code>remote_smtp:</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;driver&nbsp;=&nbsp;smtp</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;hosts&nbsp;=&nbsp;192.168.2.1</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;hosts_override</code><br>
<code>local_delivery:</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;driver&nbsp;=&nbsp;appendfile</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;file&nbsp;=&nbsp;/var/spool/mail/${local_part}</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;delivery_date_add</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;envelope_to_add</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;return_path_add</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;group&nbsp;=&nbsp;mail</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;mode_fail_narrower&nbsp;=</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;mode&nbsp;=&nbsp;0660</code><br>
<code>end</code><br>
<code>&nbsp;</code><br>
<code>######################&nbsp;DIRECTORS&nbsp;CONFIGURATION&nbsp;#######################</code><br>
<code>localuser:</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;driver&nbsp;=&nbsp;localuser</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;transport&nbsp;=&nbsp;local_delivery</code><br>
<code>end</code><br>
<code>&nbsp;</code><br>
<code>######################&nbsp;ROUTERS&nbsp;CONFIGURATION&nbsp;#########################</code><br>
<code>lookuphost:</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;driver&nbsp;=&nbsp;lookuphost</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;transport&nbsp;=&nbsp;remote_smtp</code><br>
<code>literal:</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;driver&nbsp;=&nbsp;ipliteral</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;transport&nbsp;=&nbsp;remote_smtp</code><br>
<code>end</code><br>
<code>&nbsp;</code><br>
<code>######################&nbsp;RETRY&nbsp;CONFIGURATION&nbsp;###########################</code><br>
<code>*&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;F,2h,15m&#059;&nbsp;G,16h,1h,1.5&#059;&nbsp;F,4d,8h</code><br>
<code>end</code><br>
<code>&nbsp;</code><br>
<code>######################&nbsp;REWRITE&nbsp;CONFIGURATION&nbsp;#########################</code><br>
<code>*@cericon.cranzgot.co.za&nbsp;&nbsp;psheer@cranzgot.co.za</code><br>
</FONT></TD></TR></TABLE><P>

<P>

<H2><A NAME="SECTION003331000000000000000">
30.3.1 Global settings</A>
</H2>

<P>
The <TT>
<FONT COLOR="#0000ff">exim</FONT></TT> config file is divided into six logical sections
separated by the <TT>
<FONT COLOR="#0000ff">end</FONT></TT> keyword. The top or <TT>
<FONT COLOR="#0000ff">MAIN</FONT></TT> section
contains global settings. The global settings have the following meanings:
<DL>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">log_subject</FONT></TT></STRONG></DT>
<DD>Tells <TT>
<FONT COLOR="#0000ff">exim</FONT></TT> to log the subject in the mail log file.
For example, <TT>
<FONT COLOR="#0000ff">T="I LOVE YOU"</FONT></TT> will be added to the log file.

</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">errors_address</FONT></TT></STRONG></DT>
<DD>The mail address where errors are to be sent. It doesn't
matter what you put here, because all mail will get rewritten to <TT>
<FONT COLOR="#0000ff">psheer@cranzgot.co.za</FONT></TT>,
as we see later.

</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">freeze_tell_mailmaster</FONT></TT></STRONG></DT>
<DD>Tells <TT>
<FONT COLOR="#0000ff">errors_address</FONT></TT> about <I>frozen</I> messages.
<I>frozen</I> messages are messages that could not be delivered for some reason (like
a permissions problem, or a failed message whose return address is invalid) and are
flagged to sit idly in the mail queue, and not be processed any further. Note
that frozen messages sometimes mean that something is wrong with your system
or mail configuration.

</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">local_domains</FONT></TT></STRONG></DT>
<DD>Each mail message received is processed in one of
two ways: by either a local or remote delivery. A local delivery is one to a
user on the local machine, and a remote delivery is one to somewhere else on
the Internet.
<TT>
<FONT COLOR="#0000ff">local_domains</FONT></TT> distinguishes between these two. For example, according to
the config line above, a message destined to <TT>
<FONT COLOR="#0000ff">psheer@localhost</FONT></TT> or
<TT>
<FONT COLOR="#0000ff">psheer@cericon.cranzgot.co.za</FONT></TT> is local, whereas a message to
<TT>
<FONT COLOR="#0000ff">psheer@elsewhere.co.za</FONT></TT> is remote. Note that the list is
colon delimited.
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">never_users</FONT></TT></STRONG></DT>
<DD>Never become this user. Just for security.

</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">exim_user</FONT></TT></STRONG></DT>
<DD>Specifies the user that <TT>
<FONT COLOR="#0000ff">exim</FONT></TT> should run as.

</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">exim_group</FONT></TT></STRONG></DT>
<DD>Specifies the group that <TT>
<FONT COLOR="#0000ff">exim</FONT></TT> should run as.

</DD>
</DL>
<DIV ALIGN="CENTER">

<TABLE width="100%" border="0" cellspacing="0" cellpadding="0">
<TR><TD bgcolor="#FFE0FF">
<I>It is important to understand the <TT>
<FONT COLOR="#0000ff">host_accept_relay</FONT></TT> and <TT>
<FONT COLOR="#0000ff">relay_domains</FONT></TT> options for security.</I>

</TD></TR>
</TABLE>

</DIV>
<DL>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">host_accept_relay</FONT></TT></STRONG></DT>
<DD>This option specifies machines that are allowed to use
<TT>
<FONT COLOR="#0000ff">cericon.cranzgot.co.za</FONT></TT> as a <I>relay</I>. A relay is a host
that sends mail on another machine's behalf: that is, we are acting as
a relay when we process a mail message that neither originated from
our machine nor is destined for a user on our machine.

<P>
We <I>never</I> want to relay from an untrusted host.
Why? Because it may, for example, allow someone to send 100,000
messages to 100,000 different addresses, each with <I>us</I> in the
message header.

<P>
<TT>
<FONT COLOR="#0000ff">host_accept_relay</FONT></TT> specifies a list of trusted hosts that
are allowed to send such arbitrary messages through us. Note again
that the list is colon delimited. In this example, we don't even
need to put in addresses of other machines on our LAN, except if
we are feeling friendly.

<P>
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">relay_domains</FONT></TT></STRONG></DT>
<DD><TT>
<FONT COLOR="#0000ff">relay_domains</FONT></TT> gives an additional condition for which
an arbitrary host is allowed to use us as a relay. Consider that we are a
backup mail server for a particular domain; mail to the domain does
not originate from us nor is destined for us yet must be allowed
<I>only if the destination address matches the domains for which
we are a backup</I>. We put such domains under <TT>
<FONT COLOR="#0000ff">relay_domains</FONT></TT>.
</DD>
</DL>

<P>

<H2><A NAME="SECTION003332000000000000000">
30.3.2 Transports</A>
</H2>

<P>
<A NAME="sec:eximtransports"></A>
<P>
The transport section comes immediately after the main configuration
options. It defines various <I>methods</I> of delivering mail. We are 
going to refer to these methods later in the configuration file. Our manual
<TT>
<FONT COLOR="#0000ff">telnet</FONT></TT>ing to port 25 was <I>transport</I>ing a mail message by
SMTP. Appending a mail message to the end of a mail folder is also
a transport method. These are represented by the
<TT>
<FONT COLOR="#0000ff">remote_smtp:</FONT></TT> and <TT>
<FONT COLOR="#0000ff">local_delivery:</FONT></TT> labels, respectively.

<P>
<DL>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">remote_smtp:</FONT></TT></STRONG></DT>
<DD>This transport has the following suboptions:
<DL>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">driver</FONT></TT></STRONG></DT>
<DD>The actual method of delivery. <TT>
<FONT COLOR="#0000ff">driver&nbsp;=</FONT></TT>
always specifies the kind of transport, director, or router.
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">hosts_override</FONT></TT> and <TT>
<FONT COLOR="#0000ff">hosts</FONT></TT></STRONG></DT>
<DD>Using these two options together overrides any list of hosts that may have
been looked up by DNS MX queries. By ``list of hosts'' we mean
machines established from the recipients email address to
which we might like to make an SMTP delivery, but which we are
not going to use. Instead we send all mail to <TT>
<FONT COLOR="#0000ff">192.168.2.1</FONT></TT>,
which is this company's internal mail server.
</DD>
</DL>

<P>
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">local_delivery:</FONT></TT></STRONG></DT>
<DD>This transport has the following suboptions:
<DL>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">driver</FONT></TT></STRONG></DT>
<DD>The actual method of delivery. <TT>
<FONT COLOR="#0000ff">driver&nbsp;=</FONT></TT>
always specifies the kind of transport, director, or router.

</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">file</FONT></TT></STRONG></DT>
<DD>The file to append the mail message to. <TT>
<FONT COLOR="#0000ff">$&#123;local_part&#125;</FONT></TT>
is replaced with everything before the <TT>
<FONT COLOR="#0000ff">@</FONT></TT> character of the recipient's
address.
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">delivery_date_add</FONT></TT>, <TT>
<FONT COLOR="#0000ff">envelope_to_add</FONT></TT>, and <TT>
<FONT COLOR="#0000ff">return_path_add</FONT></TT></STRONG></DT>
<DD>Various things to add to the header.
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">group</FONT></TT>, <TT>
<FONT COLOR="#0000ff">mode_fail_narrower</FONT></TT> and <TT>
<FONT COLOR="#0000ff">mode</FONT></TT></STRONG></DT>
<DD>Various permission settings.
</DD>
</DL>
</DD>
</DL>

<P>
(It should be obvious at this stage what these two transports
are going to be used for. As far as MTAs are concerned, the only
two things that ever happen to an email message are that it either (a)
gets sent through SMTP to another host or (b) gets appended to a file.)

<P>

<H2><A NAME="SECTION003333000000000000000">
30.3.3 Directors</A>
</H2>

<P>
If a message arrives and it is listed in <TT>
<FONT COLOR="#0000ff">local_domains</FONT></TT>,
<TT>
<FONT COLOR="#0000ff">exim</FONT></TT> will attempt a local delivery. This means <TT>
<FONT COLOR="#0000ff">exim</FONT></TT> works through
the list of <I>directors</I> until it finds one that does not fail. The
only director listed here is the one labeled <TT>
<FONT COLOR="#0000ff">localuser:</FONT></TT> with
<TT>
<FONT COLOR="#0000ff">local_delivery</FONT></TT> as its transport. So quite simply, email messages
having recipient addresses that are listed under <TT>
<FONT COLOR="#0000ff">local_domains</FONT></TT> are
appended to a user's mailbox file--not very complicated.

<P>
A director <I>directs</I> mail to a mailbox.

<P>

<H2><A NAME="SECTION003334000000000000000">
30.3.4 Routers</A>
</H2>

<P>
If a message arrives and it is not listed in <TT>
<FONT COLOR="#0000ff">local_domains</FONT></TT>,
<TT>
<FONT COLOR="#0000ff">exim</FONT></TT> attempts a remote delivery. Similarly, this means <TT>
<FONT COLOR="#0000ff">exim</FONT></TT>
works through the list of <I>routers</I> until it finds one that does not fail.

<P>
Two routers are listed here. The first is for common
email addresses. It uses the <TT>
<FONT COLOR="#0000ff">lookuphost</FONT></TT> driver, which
does a DNS MX query on the domain part of the email address
(i.e., everything after the <TT>
<FONT COLOR="#0000ff">@</FONT></TT>). The MX records found are
then passed to the <TT>
<FONT COLOR="#0000ff">remote_smtp</FONT></TT> transport (and in our case, then
ignored). The <TT>
<FONT COLOR="#0000ff">lookuphost</FONT></TT> driver will fail if the domain part of
the email address is a bracketed literal IP address.

<P>
The second router uses the <TT>
<FONT COLOR="#0000ff">ipliteral</FONT></TT> driver. It
sends mail directly to an IP address in the case of bracketed, literal
email addresses. For example, <TT>
<FONT COLOR="#0000ff">root@[111.1.1.1]</FONT></TT>.

<P>
A router <I>routes</I> mail to another host.

<P>

<H1><A NAME="SECTION003340000000000000000">
30.4 Full-blown Mail server</A>
</H1>

<P>
An actual mail server config file contains very little extra. This one is
the example config file that comes by default with <TT>
<FONT COLOR="#0000ff">exim-3.16</FONT></TT>:

<P>

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>10</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>15</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>20</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>25</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>30</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>35</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>40</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>45</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>50</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>55</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>60</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>65</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>70</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>75</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>80</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>####################&nbsp;MAIN&nbsp;CONFIGURATION&nbsp;SETTINGS&nbsp;#####################</code><br>
<code>#&nbsp;primary_hostname&nbsp;=</code><br>
<code>#&nbsp;qualify_domain&nbsp;=</code><br>
<code>#&nbsp;qualify_recipient&nbsp;=</code><br>
<code>#&nbsp;local_domains&nbsp;=</code><br>
<code>never_users&nbsp;=&nbsp;root</code><br>
<code>#&nbsp;host_accept_relay&nbsp;=&nbsp;localhost</code><br>
<code>#&nbsp;host_accept_relay&nbsp;=&nbsp;my.friends.host&nbsp;:&nbsp;131.111.0.0/16</code><br>
<code>#&nbsp;relay_domains&nbsp;=&nbsp;my.equivalent.domains&nbsp;:&nbsp;more.equivalent.domains</code><br>
<code>host_lookup&nbsp;=&nbsp;0.0.0.0/0</code><br>
<code>#&nbsp;receiver_unqualified_hosts&nbsp;=</code><br>
<code>#&nbsp;sender_unqualified_hosts&nbsp;=</code><br>
<code>rbl_domains&nbsp;=&nbsp;rbl.maps.vix.com</code><br>
<code>no_rbl_reject_recipients</code><br>
<code>sender_reject&nbsp;=&nbsp;"*@*.sex*.net:*@sex*.net"</code><br>
<code>host_reject&nbsp;=&nbsp;"open-relay.spamming-site.com"</code><br>
<code>rbl_warn_header</code><br>
<code>#&nbsp;rbl_domains&nbsp;=&nbsp;rbl.maps.vix.com:dul.maps.vix.com:relays.orbs.org</code><br>
<code>#&nbsp;percent_hack_domains&nbsp;=&nbsp;*</code><br>
<code>end</code><br>
<code>######################&nbsp;TRANSPORTS&nbsp;CONFIGURATION&nbsp;######################</code><br>
<code>remote_smtp:</code><br>
<code>&nbsp;&nbsp;driver&nbsp;=&nbsp;smtp</code><br>
<code>#&nbsp;procmail&nbsp;transport&nbsp;goes&nbsp;here&nbsp;&#060;---</code><br>
<code>local_delivery:</code><br>
<code>&nbsp;&nbsp;driver&nbsp;=&nbsp;appendfile</code><br>
<code>&nbsp;&nbsp;file&nbsp;=&nbsp;/var/spool/mail/${local_part}</code><br>
<code>&nbsp;&nbsp;delivery_date_add</code><br>
<code>&nbsp;&nbsp;envelope_to_add</code><br>
<code>&nbsp;&nbsp;return_path_add</code><br>
<code>&nbsp;&nbsp;group&nbsp;=&nbsp;mail</code><br>
<code>&nbsp;&nbsp;mode&nbsp;=&nbsp;0660</code><br>
<code>address_pipe:</code><br>
<code>&nbsp;&nbsp;driver&nbsp;=&nbsp;pipe</code><br>
<code>&nbsp;&nbsp;return_output</code><br>
<code>address_file:</code><br>
<code>&nbsp;&nbsp;driver&nbsp;=&nbsp;appendfile</code><br>
<code>&nbsp;&nbsp;delivery_date_add</code><br>
<code>&nbsp;&nbsp;envelope_to_add</code><br>
<code>&nbsp;&nbsp;return_path_add</code><br>
<code>address_reply:</code><br>
<code>&nbsp;&nbsp;driver&nbsp;=&nbsp;autoreply</code><br>
<code>end</code><br>
<code>######################&nbsp;DIRECTORS&nbsp;CONFIGURATION&nbsp;#######################</code><br>
<code>#&nbsp;routers&nbsp;because&nbsp;of&nbsp;a&nbsp;"self=local"&nbsp;setting&nbsp;(not&nbsp;used&nbsp;in&nbsp;this&nbsp;configuration).</code><br>
<code>system_aliases:</code><br>
<code>&nbsp;&nbsp;driver&nbsp;=&nbsp;aliasfile</code><br>
<code>&nbsp;&nbsp;file&nbsp;=&nbsp;/etc/aliases</code><br>
<code>&nbsp;&nbsp;search_type&nbsp;=&nbsp;lsearch</code><br>
<code>&nbsp;&nbsp;user&nbsp;=&nbsp;mail</code><br>
<code>&nbsp;&nbsp;group&nbsp;=&nbsp;mail</code><br>
<code>&nbsp;&nbsp;file_transport&nbsp;=&nbsp;address_file</code><br>
<code>&nbsp;&nbsp;pipe_transport&nbsp;=&nbsp;address_pipe</code><br>
<code>userforward:</code><br>
<code>&nbsp;&nbsp;driver&nbsp;=&nbsp;forwardfile</code><br>
<code>&nbsp;&nbsp;file&nbsp;=&nbsp;.forward</code><br>
<code>&nbsp;&nbsp;no_verify</code><br>
<code>&nbsp;&nbsp;no_expn</code><br>
<code>&nbsp;&nbsp;check_ancestor</code><br>
<code>#&nbsp;filter</code><br>
<code>&nbsp;&nbsp;file_transport&nbsp;=&nbsp;address_file</code><br>
<code>&nbsp;&nbsp;pipe_transport&nbsp;=&nbsp;address_pipe</code><br>
<code>&nbsp;&nbsp;reply_transport&nbsp;=&nbsp;address_reply</code><br>
<code>#&nbsp;procmail&nbsp;director&nbsp;goes&nbsp;here&nbsp;&#060;---</code><br>
<code>localuser:</code><br>
<code>&nbsp;&nbsp;driver&nbsp;=&nbsp;localuser</code><br>
<code>&nbsp;&nbsp;transport&nbsp;=&nbsp;local_delivery</code><br>
<code>end</code><br>
<code>######################&nbsp;ROUTERS&nbsp;CONFIGURATION&nbsp;#########################</code><br>
<code>#&nbsp;widen_domains&nbsp;=&nbsp;"sales.mycompany.com:mycompany.com"</code><br>
<code>lookuphost:</code><br>
<code>&nbsp;&nbsp;driver&nbsp;=&nbsp;lookuphost</code><br>
<code>&nbsp;&nbsp;transport&nbsp;=&nbsp;remote_smtp</code><br>
<code>#&nbsp;widen_domains&nbsp;=&nbsp;</code><br>
<code>literal:</code><br>
<code>&nbsp;&nbsp;driver&nbsp;=&nbsp;ipliteral</code><br>
<code>&nbsp;&nbsp;transport&nbsp;=&nbsp;remote_smtp</code><br>
<code>end</code><br>
<code>######################&nbsp;RETRY&nbsp;CONFIGURATION&nbsp;###########################</code><br>
<code>*&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;F,2h,15m&#059;&nbsp;G,16h,1h,1.5&#059;&nbsp;F,4d,8h</code><br>
<code>end</code><br>
<code>######################################################################</code><br>
</FONT></TD></TR></TABLE><P>

<P>
For <TT>
<FONT COLOR="#0000ff">procmail</FONT></TT>  support (see
<TT>
<FONT COLOR="#0000ff">procmail</FONT></TT>(1), <TT>
<FONT COLOR="#0000ff">procmailrc</FONT></TT>(6), and <TT>
<FONT COLOR="#0000ff">procmailex</FONT></TT>(5)), simply add

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>procmail:</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;driver&nbsp;=&nbsp;pipe</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;command&nbsp;=&nbsp;"/usr/bin/procmail&nbsp;-Y&nbsp;-d&nbsp;${local_part}"</code><br>
</FONT></TD></TR></TABLE><P>
after your <TT>
<FONT COLOR="#0000ff">remote_smtp</FONT></TT> transport, and then also,

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>procmail:</code><br>
<code>&nbsp;&nbsp;driver&nbsp;=&nbsp;localuser</code><br>
<code>&nbsp;&nbsp;transport&nbsp;=&nbsp;procmail</code><br>
<code>&nbsp;&nbsp;require_files&nbsp;=&nbsp;/usr/bin/procmail</code><br>
</FONT></TD></TR></TABLE><P>
after your <TT>
<FONT COLOR="#0000ff">user_forward</FONT></TT> director.

<P>

<H1><A NAME="SECTION003350000000000000000">
30.5 Shell Commands for <TT>
<FONT COLOR="#0000ff">exim</FONT></TT> Administration</A>
</H1>

<P>
As with other daemons, you can stop <TT>
<FONT COLOR="#0000ff">exim</FONT></TT>, start <TT>
<FONT COLOR="#0000ff">exim</FONT></TT>, and
cause <TT>
<FONT COLOR="#0000ff">exim</FONT></TT> to reread its configuration file with:

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>/etc/init.d/exim&nbsp;stop</code><br>
<code>/etc/init.d/exim&nbsp;start</code><br>
<code>/etc/init.d/exim&nbsp;reload</code><br>
</FONT></TD></TR></TABLE><P>
You should always do a <TT>
<FONT COLOR="#0000ff">reload</FONT></TT> to cause config
file changes to take effect. The <TT>
<FONT COLOR="#0000ff">start</FONT></TT>up script
actually just runs <TT>
<FONT COLOR="#0000ff">exim -bd -q30m</FONT></TT>, which tells
<TT>
<FONT COLOR="#0000ff">exim</FONT></TT> to start as a standalone daemon, listening for
connections on port 25, and then execute a <TT>
<FONT COLOR="#0000ff">runq</FONT></TT> (explained
below) every 30 minutes.

<P>
To cause <TT>
<FONT COLOR="#0000ff">exim</FONT></TT> <FONT COLOR="#ffa500">[and many other MTAs for
that matter]</FONT> to loop through the queue of pending messages
and consider each one for deliver, run

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>runq</code><br>
</FONT></TD></TR></TABLE><P>
which is the same as <TT>
<FONT COLOR="#0000ff">exim -q</FONT></TT>.

<P>
To list mail that is queued for delivery, use

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>mailq</code><br>
</FONT></TD></TR></TABLE><P>
which is the same as <TT>
<FONT COLOR="#0000ff">exim -bp</FONT></TT>.

<P>
To forcibly attempt delivery on any mail in the queue, use

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>exim&nbsp;-qf</code><br>
</FONT></TD></TR></TABLE><P>
and then to forcibly retry even frozen messages in the queue, use

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>exim&nbsp;-qff</code><br>
</FONT></TD></TR></TABLE><P>

<P>
To delete a message from the queue, use

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>exim&nbsp;-Mrm&nbsp;&#060;message-id&#062;</code><br>
</FONT></TD></TR></TABLE><P>

<P>
The man page <TT>
<FONT COLOR="#0000ff">exim</FONT></TT>(8) contains exhaustive treatment
of command-line options. Those above are most of what you will use,
however.

<P>

<H1><A NAME="SECTION003360000000000000000">
30.6 The Queue</A>
</H1>

<P>
It is often useful to check the queue directory
<TT>
<FONT COLOR="#0000ff">/var/spool/exim/input/</FONT></TT>
for mail messages, just to get an inside look at what's going on. The simple
session--

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>10</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>[root@cericon]#&nbsp;<font color="navy"><B>mailq</B></font></code><br>
<code>&nbsp;0m&nbsp;&nbsp;&nbsp;320&nbsp;14Epss-0008DY-00&nbsp;&#060;psheer@cranzgot.co.za&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;freddy@elmstreet.org</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;0m&nbsp;&nbsp;&nbsp;304&nbsp;14Ept8-0008Dg-00&nbsp;&#060;psheer@cranzgot.co.za&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;igor@ghostbusters.com</code><br>
<code>&nbsp;</code><br>
<code>[root@cericon]#&nbsp;<font color="navy"><B>ls&nbsp;-l&nbsp;/var/spool/exim/input/</B></font></code><br>
<code>total&nbsp;16</code><br>
<code>-rw-------&nbsp;&nbsp;&nbsp;&nbsp;1&nbsp;root&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;root&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;25&nbsp;Jan&nbsp;&nbsp;6&nbsp;11:43&nbsp;14Epss-0008DY-00-D</code><br>
<code>-rw-------&nbsp;&nbsp;&nbsp;&nbsp;1&nbsp;root&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;root&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;550&nbsp;Jan&nbsp;&nbsp;6&nbsp;11:43&nbsp;14Epss-0008DY-00-H</code><br>
<code>-rw-------&nbsp;&nbsp;&nbsp;&nbsp;1&nbsp;root&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;root&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;25&nbsp;Jan&nbsp;&nbsp;6&nbsp;11:43&nbsp;14Ept8-0008Dg-00-D</code><br>
<code>-rw-------&nbsp;&nbsp;&nbsp;&nbsp;1&nbsp;root&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;root&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;530&nbsp;Jan&nbsp;&nbsp;6&nbsp;11:43&nbsp;14Ept8-0008Dg-00-H</code><br>
</FONT></TD></TR></TABLE><P>
--clearly shows that two messages are queued for delivery. The
files ending in <TT>
<FONT COLOR="#0000ff">-H</FONT></TT> are <I>envelope headers</I>, and those ending in <TT>
<FONT COLOR="#0000ff">-D</FONT></TT>
are message bodies. The <TT>
<FONT COLOR="#0000ff">spec.txt</FONT></TT> document will show you how to
interpret the contents of the header files.

<P>
Don't be afraid to manually <TT>
<FONT COLOR="#0000ff">rm</FONT></TT> files from this directory, but
always delete them in pairs (i.e., remove the both the header <I>and</I> the
body file), and make sure <TT>
<FONT COLOR="#0000ff">exim</FONT></TT> is not running at the time.
In the above example, the commands,

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>[root@cericon]#&nbsp;<font color="navy"><B>exim&nbsp;-Mrm&nbsp;14Epss-0008DY-00&nbsp;14Ept8-0008Dg-00</B></font></code><br>
<code>Message&nbsp;14Epss-0008DY-00&nbsp;has&nbsp;been&nbsp;removed</code><br>
<code>Message&nbsp;14Ept8-0008Dg-00&nbsp;has&nbsp;been&nbsp;removed</code><br>
<code>[root@cericon]#&nbsp;<font color="navy"><B>mailq</B></font></code><br>
<code>[root@cericon]#&nbsp;</code><br>
</FONT></TD></TR></TABLE><P>
work even better.

<P>

<H1><A NAME="SECTION003370000000000000000">
30.7 <TT>
<FONT COLOR="#0000ff">/etc/aliases</FONT></TT> for Equivalent Addresses</A>
</H1>

<P>
Often, we would like certain local addresses to <I>actually</I>
deliver to other addresses. For instance, we would like all
mail destined to user <TT>
<FONT COLOR="#0000ff">MAILER-DAEMON</FONT></TT> to actually go
to user <TT>
<FONT COLOR="#0000ff">postmaster</FONT></TT>; or perhaps some user has two
accounts but would like to read mail from only one of them.

<P>
The <TT>
<FONT COLOR="#0000ff">/etc/aliases</FONT></TT> file performs this mapping. This
file has become somewhat of an institution; however you
can see that in the case of <TT>
<FONT COLOR="#0000ff">exim</FONT></TT>, aliasing is
completely arbitrary: you can specify a lookup on <I>any</I>
file under the <TT>
<FONT COLOR="#0000ff">system_aliases:</FONT></TT> director provided
that file is colon delimited.

<P>
A default <TT>
<FONT COLOR="#0000ff">/etc/aliases</FONT></TT> file could contain as much as the following;
you should check that the <TT>
<FONT COLOR="#0000ff">postmaster</FONT></TT> account does
exist on your system, and test whether you can read, send, and
receive mail as user <TT>
<FONT COLOR="#0000ff">postmaster</FONT></TT>.

<P>

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>10</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>15</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>20</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>25</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>30</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>35</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>40</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>45</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>#&nbsp;This&nbsp;is&nbsp;a&nbsp;combination&nbsp;of&nbsp;what&nbsp;I&nbsp;found&nbsp;in&nbsp;the&nbsp;Debian</code><br>
<code>#&nbsp;and&nbsp;RedHat&nbsp;distributions.</code><br>
<code>&nbsp;</code><br>
<code>MAILER-DAEMON:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>abuse:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>anonymous:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>backup:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>backup-reports:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>bin:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>daemon:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>decode:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>dns:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>dns-admin:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>dumper:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>fetchmail-daemon:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>games:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>gnats:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>ingres:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>info:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>irc:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>list:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>listmaster:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>lp:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>mail:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>mailer-daemon:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>majordom:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>man:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>manager:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>msql:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>news:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>nobody:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>operator:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>postgres:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>proxy:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>root:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>sync:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>support:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>sys:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>system:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>toor:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>uucp:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>warnings:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>web-master:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>www-data:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;postmaster</code><br>
<code>&nbsp;</code><br>
<code>#&nbsp;some&nbsp;users&nbsp;who&nbsp;want&nbsp;their&nbsp;mail&nbsp;redirected</code><br>
<code>arny:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;mail@swartzneger.co.us</code><br>
<code>larry:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;lking@cnn.com</code><br>
</FONT></TD></TR></TABLE><P>

<P>
You can remove a lot of these aliases, since they assume services
to be running that might not be installed--<TT>
<FONT COLOR="#0000ff">games</FONT></TT>, <TT>
<FONT COLOR="#0000ff">ingres</FONT></TT>,
for example. Aliases can do two things: firstly, anticipate what mail
people are likely to use if they need to contact the administrator;
and secondly, catch any mail sent by system daemons: for
example the, email address of the DNS administrator is dictated
by the DNS config files, as explained on page <A HREF="node43.html#page:dnsemail"><IMG  ALIGN="BOTTOM" BORDER="1" ALT="[*]" SRC="crossref.png"></A>.

<P>
Note that an alias in the <TT>
<FONT COLOR="#0000ff">/etc/aliases</FONT></TT> file does not have to
have an account on the system--<TT>
<FONT COLOR="#0000ff">larry</FONT></TT> and <TT>
<FONT COLOR="#0000ff">arny</FONT></TT> need
not have entries in the <TT>
<FONT COLOR="#0000ff">/etc/passwd</FONT></TT> file.

<P>

<H1><A NAME="SECTION003380000000000000000">
30.8 Real-Time Blocking List -- Combating Spam</A>
</H1>

<P>

<H2><A NAME="SECTION003381000000000000000">
30.8.1 What is <I>spam</I>?</A>
</H2>

<P>

<I>Spam</I> refers to unsolicited <FONT COLOR="#ffa500">[Not looked for or requested; unsought]</FONT>bulk mail sent to users usually for promotional purposes. That is, mail
is sent automatically to many people with whom the sender has no
relationship, and where the recipient did nothing to prompt the
mail: all on the <I>chance</I> that the recipient might be interested in the
subject matter.

<P>
Alternatively, spam can be thought of as any mail sent
to email addresses, where those addresses were obtained without
their owners consent. More practically, anyone who has had an
email account for very long will have gotten messages like
<TT>
<FONT COLOR="#0000ff">Subject: Fast way to earn big $$$!</FONT></TT>, which clutters my
mailbox. The longer you have an email address, the more of these
messages you will get, and the more irritated you will get.

<P>
To send spam is easy. Work your way around the Internet till you
find a mail server that allows relaying. Then send it 10,000 email
addresses and a message about where to get pictures of naked
underage girls. Now you are a genuine worthy-of-being-arrested
spammer. Unfortunately for the unsuspecting administrator of that
machine and provided you have even a little clue what you're
doing, he will probably never be able to track you down. Several
other tricks are employed to get the most out of your
$100-for-1,000,000-genuine-email-addresses.

<P>
Note that spam is not merely email you are not interested in. People
often confuse mail with other types of communication... like
telephone calls: if you get a telephone call, you <I>have</I> to pick
up the phone then and there--the call is an an invasion of your
privacy. The beauty of email is that you never need to have your
privacy invaded. You can simply delete the mail. If you never want
to get email from a particular person again, you can simply add a
filter that blocks mail from that person's address (see <TT>
<FONT COLOR="#0000ff">procmailex</FONT></TT>(5)).
 <FONT COLOR="#ffa500">[If you are irritated by the presumption of the sender, then that's
<I>your</I> problem. Replying to that person with ``Please don't email me...''
not only shows that you are insecure, but also that you are clueless, don't
get much mail, and are therefore also unpopular.]</FONT>
<P>
The point at which email becomes intrusive is purely a question
of volume, much like airwave advertisements. <I>Because it comes
from a different place each time, you cannot protect yourself against
it with a simple mail filter.</I>

<P>
Typical spam mail will begin with a spammer
subject like <TT>
<FONT COLOR="#0000ff">Create Wealth From Home Now!!</FONT></TT> and then
the spammer will audaciously append the footer:

<P>

<BLOCKQUOTE><FONT SIZE="-1">This is not a SPAM. You are receiving this because
you are on a list of email addresses that I have bought.
And you have opted to receive information about
business opportunities. If you did not opt in to receive
information on business opportunities then please accept
our apology. To be REMOVED from this list simply reply
with REMOVE as the subject. And you will NEVER receive
another email from me.
</FONT></BLOCKQUOTE>

<P>
Need I say that you should be wary of replying with <TT>
<FONT COLOR="#0000ff">REMOVE</FONT></TT>,
since it clearly tells the sender that your email is a valid address.

<P>

<H2><A NAME="SECTION003382000000000000000">
30.8.2 Basic spam prevention</A>
</H2>

<P>
You can start by at least adding the following lines to your
<TT>
<FONT COLOR="#0000ff">MAIN</FONT></TT> configuration section:

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>headers_check_syntax</code><br>
<code>headers_sender_verify</code><br>
<code>sender_verify</code><br>
<code>receiver_verify</code><br>
</FONT></TD></TR></TABLE><P>
The option <TT>
<FONT COLOR="#0000ff">headers_check_syntax</FONT></TT> causes <TT>
<FONT COLOR="#0000ff">exim</FONT></TT> to
check all headers of incoming mail messages for correct syntax,
failing them otherwise. The next three options check that one of the
<TT>
<FONT COLOR="#0000ff">Sender:</FONT></TT>, <TT>
<FONT COLOR="#0000ff">Reply-To:</FONT></TT> or <TT>
<FONT COLOR="#0000ff">From:</FONT></TT> headers, as well
as both the addresses in the SMTP <TT>
<FONT COLOR="#0000ff">MAIL</FONT></TT> and <TT>
<FONT COLOR="#0000ff">RCPT</FONT></TT>
commands, are genuine email
addresses.

<P>
The reasoning here is that spammers will often use
malformed headers to trick the MTA into sending things it ordinarily
wouldn't, I am not sure exactly how this applies in <TT>
<FONT COLOR="#0000ff">exim</FONT></TT>'s
case, but these are for the good measure of rejecting email
messages at the point where the SMTP exchange is being initiated.

<P>

<H2><A NAME="SECTION003383000000000000000">
30.8.3 Real-time blocking list</A>
</H2>

<P>
To find out a lot more about spamming, banning hosts,
reporting spam and email usage in general,
see
<EM>MAPS (Mail Abuse Prevention
System LLC)</EM> <I>&lt;<TT><A NAME="tex2html44"
  HREF="http://www.mail-abuse.org/">http://www.mail-abuse.org/</A></TT>&gt;</I>, as well as <EM>Open Relay
Behavior-modification System</EM> <I>&lt;<TT><A NAME="tex2html45"
  HREF="http://www.orbs.org/">http://www.orbs.org/</A></TT>&gt;</I>. <FONT COLOR="#ffa500">[If this site is not working,
there is also <I><TT><A NAME="tex2html46"
  HREF="http://www.orbl.org/">http://www.orbl.org/</A></TT></I> and
<I><TT><A NAME="tex2html47"
  HREF="http://www.ordb.org/">http://www.ordb.org/</A></TT></I>.]</FONT><I>Real-time Blocking Lists</I>
or RBL's are a not-so-new idea that has been
incorporated into <TT>
<FONT COLOR="#0000ff">exim</FONT></TT> as a feature. It works as follows. The
spammer has to use a host that allows relays. The IP of that
relay host will be clear to the MTA at the time of connection. The
MTA can then check that against a database of publicly available
<I>banned IP addresses</I> of relay hosts. For <TT>
<FONT COLOR="#0000ff">exim</FONT></TT>, this
means the list under <TT>
<FONT COLOR="#0000ff">rbl_domains</FONT></TT>. If the <TT>
<FONT COLOR="#0000ff">rbl_domains</FONT></TT>
friendly has this IP blacklisted, then <TT>
<FONT COLOR="#0000ff">exim</FONT></TT> denies it also.
You can enable this capability with <FONT COLOR="#ffa500">[This example comes
from <TT>
<FONT COLOR="#0000ff">exim</FONT></TT>'s front web page.]</FONT>
<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>10</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>#&nbsp;reject&nbsp;messages&nbsp;whose&nbsp;sending&nbsp;host&nbsp;is&nbsp;in&nbsp;MAPS/RBL</code><br>
<code>#&nbsp;add&nbsp;warning&nbsp;to&nbsp;messages&nbsp;whose&nbsp;sending&nbsp;host&nbsp;is&nbsp;in&nbsp;ORBS</code><br>
<code>rbl_domains&nbsp;=&nbsp;blackholes.mail-abuse.org/reject&nbsp;:&nbsp;\</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;dialups.mail-abuse.org/reject&nbsp;:&nbsp;\</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;relays.mail-abuse.org/reject&nbsp;:&nbsp;\</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;relays.orbs.org/warn</code><br>
<code>#&nbsp;check&nbsp;all&nbsp;hosts&nbsp;other&nbsp;than&nbsp;those&nbsp;on&nbsp;internal&nbsp;network</code><br>
<code>rbl_hosts&nbsp;=&nbsp;!192.168.0.0/16:0.0.0.0/0</code><br>
<code>#&nbsp;but&nbsp;allow&nbsp;mail&nbsp;to&nbsp;postmaster@my.dom.ain&nbsp;even&nbsp;from&nbsp;rejected&nbsp;host</code><br>
<code>recipients_reject_except&nbsp;=&nbsp;postmaster@my.dom.ain</code><br>
<code>#&nbsp;change&nbsp;some&nbsp;logging&nbsp;actions&nbsp;(collect&nbsp;more&nbsp;data)</code><br>
<code>rbl_log_headers&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;#&nbsp;log&nbsp;headers&nbsp;of&nbsp;accepted&nbsp;RBLed&nbsp;messages</code><br>
<code>rbl_log_rcpt_count&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;#&nbsp;log&nbsp;recipient&nbsp;info&nbsp;of&nbsp;accepted&nbsp;RBLed&nbsp;messages</code><br>
</FONT></TD></TR></TABLE><P>
in your <TT>
<FONT COLOR="#0000ff">MAIN</FONT></TT> configuration section. Also remember
to remove the line <TT>
<FONT COLOR="#0000ff">no_rbl_reject_recipients</FONT></TT>; otherwise,
<TT>
<FONT COLOR="#0000ff">exim</FONT></TT> will only log a warning message and not actually refuse
email.

<P>

<H2><A NAME="SECTION003384000000000000000">
30.8.4 Mail administrator and user responsibilities</A>
</H2>

<P>
Mail administrator and email users are expected to be aware of the
following:

<UL>
<LI>Spam is evil.
</LI>
<LI>Spam is caused by poorly configured mail servers.
</LI>
<LI>It is the responsibility of the mail administrator to ensure
      that proper measures have been taken to prevent spam.
</LI>
<LI>Even as a user, you should follow up spam by checking where it came
      from and complaining to those administrators.
</LI>
<LI>Many mail administrators are not aware there is an issue.
      Remind them.
</LI>
</UL>

<P>

<H1><A NAME="SECTION003390000000000000000">
30.9 Sendmail</A>
</H1>

<P>
<TT>
<FONT COLOR="#0000ff">sendmail</FONT></TT>'s configuration file is <TT>
<FONT COLOR="#0000ff">/etc/sendmail.cf</FONT></TT>.
This file format was inherited from the first U<SMALL>NIX</SMALL> servers and
references simpler files under the directory <TT>
<FONT COLOR="#0000ff">/etc/mail/</FONT></TT>.
You can do most ordinary things by editing one or another file under
<TT>
<FONT COLOR="#0000ff">/etc/mail/</FONT></TT> without having to deal with the complexities of
<TT>
<FONT COLOR="#0000ff">/etc/sendmail.cf</FONT></TT>.

<P>
Like most stock MTAs shipped with L<SMALL>INUX</SMALL> distributions,
the <TT>
<FONT COLOR="#0000ff">sendmail</FONT></TT> package will work by default as a mailer without
any configuration. However, as always, you will have to add a list of relay
hosts. This is done in the file <TT>
<FONT COLOR="#0000ff">/etc/mail/access</FONT></TT> for <TT>
<FONT COLOR="#0000ff">sendmail-8.10</FONT></TT>
and above. To relay from yourself and, say, the hosts on network <TT>
<FONT COLOR="#0000ff">192.168.0.0/16</FONT></TT>,
as well as, say, the domain <I>hosts</I><TT>
<FONT COLOR="#0000ff">.trusted.com</FONT></TT>, you must have at least:

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>localhost.localdomain&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;RELAY</code><br>
<code>localhost&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;RELAY</code><br>
<code>127.0.0.1&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;RELAY</code><br>
<code>192.168&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;RELAY</code><br>
<code>trusted.com&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;RELAY</code><br>
</FONT></TD></TR></TABLE><P>
which is exactly what the <TT>
<FONT COLOR="#0000ff">host_accept_relay</FONT></TT> option does
in the case of <TT>
<FONT COLOR="#0000ff">exim</FONT></TT>.

<P>
The domains for which you are acting as a backup mail server must be
listed in the file 
<TT>
<FONT COLOR="#0000ff">/etc/mail/relay-domains</FONT></TT>, each on a single
line. This is analogous to the 
<TT>
<FONT COLOR="#0000ff">relay_domains</FONT></TT> option of <TT>
<FONT COLOR="#0000ff">exim</FONT></TT>.

<P>
Then, of course, the domains for which <TT>
<FONT COLOR="#0000ff">sendmail</FONT></TT> is going
to receive mail must also be specified. This is analogous to the
<TT>
<FONT COLOR="#0000ff">local_domains</FONT></TT> option of <TT>
<FONT COLOR="#0000ff">exim</FONT></TT>. These are listed in the
file 
<TT>
<FONT COLOR="#0000ff">/etc/mail/local-host-names</FONT></TT>, each on a single line.

<P>
The same <TT>
<FONT COLOR="#0000ff">/etc/aliases</FONT></TT> file is used by <TT>
<FONT COLOR="#0000ff">exim</FONT></TT>
and <TT>
<FONT COLOR="#0000ff">sendmail</FONT></TT>.

<P>
Having configured anything under <TT>
<FONT COLOR="#0000ff">/etc/mail/</FONT></TT>, you should
now run <TT>
<FONT COLOR="#0000ff">make</FONT></TT> in this directory to rebuild lookup tables
for these files. You also have to run the command <TT>
<FONT COLOR="#0000ff">newaliases</FONT></TT>
whenever you modify the <TT>
<FONT COLOR="#0000ff">/etc/aliases</FONT></TT> file. In both cases, 
you must restart <TT>
<FONT COLOR="#0000ff">sendmail</FONT></TT>.

<P>
<TT>
<FONT COLOR="#0000ff">sendmail</FONT></TT> has received a large number of security
alerts in its time. It is imperative that you install the latest version. Note
that older versions of <TT>
<FONT COLOR="#0000ff">sendmail</FONT></TT> have configurations that allowed
relaying by default--another reason to upgrade.

<P>
A useful resource to for finding out more tricks with <TT>
<FONT COLOR="#0000ff">sendmail</FONT></TT>
is <EM>The Sendmail FAQ</EM> <I>&lt;<TT><A NAME="tex2html48"
  HREF="http://www.sendmail.org/faq/">http://www.sendmail.org/faq/</A></TT>&gt;</I>.

<P>
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