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<h1><img src="postfix-logo.jpg" width="203" height="98" ALT="">Postfix
Installation From Source Code </h1>

<hr>

<h2> <a name="1">1 - Purpose of this document</a> </h2>

<p> If you are using a pre-compiled version of Postfix, you should
start with BASIC_CONFIGURATION_README and the general documentation
referenced by it.  INSTALL is only a bootstrap document to get
Postfix up and running from scratch with the minimal number of
steps; it should not be considered part of the general documentation.
</p>

<p> This document describes how to build, install and configure a
Postfix system so that it can do one of the following: </p>

<ul>

<li> Send mail only, without changing an existing Sendmail
installation.

<li> Send and receive mail via a virtual host interface, still
without any change to an existing Sendmail installation.

<li> Run Postfix instead of Sendmail.

</ul>

<p> Topics covered in this document: </p>

<ol>

<li> <a href="#1">Purpose of this document</a>

<li> <a href="#2">Typographical conventions</a>

<li> <a href="#3">Documentation</a>

<li> <a href="#4">Building on a supported system</a>

<li> <a href="#5">Porting Postfix to an unsupported system</a>

<li> <a href="#install">Installing the software after successful
compilation </a>

<li> <a href="#send_only">Configuring Postfix to send mail
only </a>

<li> <a href="#send_receive">Configuring Postfix to send and
receive mail via virtual interface </a>

<li> <a href="#replace">Running Postfix instead of Sendmail</a>

<li> <a href="#mandatory">Mandatory configuration file edits</a>

<li> <a href="#hamlet">To chroot or not to chroot</a>

<li> <a href="#care">Care and feeding of the Postfix system</a>

</ol>

<h2> <a name="2">2 - Typographical conventions</a> </h2>

<p> In the instructions below, a command written as </p>

<blockquote>
<pre>
# command
</pre>
</blockquote>

<p> should be executed as the superuser. </p>

<p> A command written as </p>

<blockquote>
<pre>
% command
</pre>
</blockquote>

<p> should be executed as an unprivileged user.  </p>

<h2> <a name="3">3 - Documentation</a> </h2>

<p> Documentation is available as README files (start with the file
README_FILES/AAAREADME), as HTML web pages (point your browser to
"html/index.html") and as UNIX-style manual pages. </p>

<p> You should view the README files with a pager such as more(1)
or less(1), because the files use backspace characters in order to
produce <b>bold</b> font. To print a README file without backspace
characters, use the col(1) command.  For example: </p>

<blockquote>
<pre>
% col -bx &lt;file | lpr
</pre>
</blockquote>

<p> In order to view the manual pages before installing Postfix,
point your MANPATH environment variable to the "man" subdirectory;
be sure to use an absolute path.  </p>

<blockquote>
<pre>
% export MANPATH; MANPATH="`pwd`/man:$MANPATH"
% setenv MANPATH "`pwd`/man:$MANPATH"
</pre>
</blockquote>

<p> Of particular interest is the postconf(5) manual page that
lists all the 500+ configuration parameters. The HTML version of
this text makes it easy to navigate around.  </p>

<p> All Postfix source files have their own built-in manual page.
Tools to extract those embedded manual pages are available in the
mantools directory. </p>

<h2> <a name="4">4 - Building on a supported system</a> </h2>

<p> At some point in time, a version of Postfix was supported on: </p>

<blockquote>
<p>
AIX 3.2.5, 4.1.x, 4.2.0, 4.3.x, 5.2 <br>
BSD/OS 2.x, 3.x, 4.x <br>
Darwin 1.x <br>
FreeBSD 2.x, 3.x, 4.x, 5.x <br>
HP-UX  9.x, 10.x, 11.x <br>
IRIX 5.x, 6.x <br>
Linux Debian 1.3.1, 2.x, 3.x <br>
Linux RedHat 3.x (January 2004) - 9.x <br>
Linux Slackware 3.x, 4.x, 7.x <br>
Linux SuSE 5.x, 6.x, 7.x <br>
Linux Ubuntu 4.10..7.04<br>
Mac OS X <br>
NEXTSTEP 3.x <br>
NetBSD 1.x <br>
OPENSTEP 4.x <br>
OSF1.V3 - OSF1.V5 (Digital UNIX) <br>
Reliant UNIX 5.x <br>
Rhapsody 5.x <br>
SunOS 4.1.4 (March 2007) <br>
SunOS 5.4 - 5.10 (Solaris 2.4..10) <br>
Ultrix 4.x (well, that was long ago) <br>
</p>
</blockquote>

<p> or something closely resemblant. </p>

<h3>4.1 - Getting started</h3>

<p> On Solaris, the "make" command and other utilities for software
development are in /usr/ccs/bin, so you MUST have /usr/ccs/bin in
your command search path. If these files do not exist, install the
development packages first. See the Solaris FAQ item "<a
href="http://www.science.uva.nl/pub/solaris/solaris2.html#q6.2">Which
packages do I need to install to support a C compiler?</a>". </p>

<p> If you need to build Postfix for multiple architectures, use the
"lndir" command to build a shadow tree with symbolic links to the
source files. "lndir" is part of X11R6. </p>

<p> If at any time in the build process you get messages like: "make:
don't know how to ..." you should be able to recover by running
the following command from the Postfix top-level directory: </p>

<blockquote>
<pre>
% make -f Makefile.init makefiles
</pre>
</blockquote>

<p> If you copied the Postfix source code after building it on another
machine, it is a good idea to cd into the top-level directory and
first do this:</p>

<blockquote>
<pre>
% make tidy
</pre>
</blockquote>

<p> This will get rid of any system dependencies left over from
compiling the software elsewhere. </p>

<h3>4.2 - What compiler to use</h3>

<p> To build with GCC, or with the native compiler if people told me
that is better for your system, just cd into the top-level Postfix
directory of the source tree and type: </p>

<blockquote>
<pre>
% make
</pre>
</blockquote>

<p> To build with a non-default compiler, you need to specify the name
of the compiler. Here are a few examples: </p>

<blockquote>
<pre>
% make makefiles CC=/opt/SUNWspro/bin/cc        (Solaris)
% make

% make makefiles CC="/opt/ansic/bin/cc -Ae"     (HP-UX)
% make

% make makefiles CC="purify cc"
% make
</pre>
</blockquote>

<p> and so on. In some cases, optimization is turned off automatically. </p>

<h3>4.3 - Building with optional extensions</h3>

By default, Postfix builds as a mail system with relatively few
bells and whistles. Support for third-party databases etc.
must be configured when Postfix is compiled.  The following documents describe how to build Postfix with support for extensions:

<blockquote>
<table border="1">

<tr> <th>Postfix extension </th> <th>Document </th> <th>Availability</th>
</tr>

<tr> <td> Berkeley DB database</td> <td>DB_README</td> <td> Postfix
1.0 </td> </tr>

<tr> <td> LDAP database</td> <td>LDAP_README</td> <td> Postfix
1.0 </td> </tr>

<tr> <td> MySQL database</td> <td>MYSQL_README</td> <td> Postfix
1.0 </td> </tr>

<tr> <td> Perl compatible regular expression</td> <td>PCRE_README</td>
<td> Postfix 1.0 </td> </tr>

<tr> <td> PostgreSQL database</td> <td>PGSQL_README</td> <td>
Postfix 2.0 </td> </tr>

<tr> <td> SASL authentication </td> <td>SASL_README</td> <td>
Postfix 1.0 </td> </tr>

<tr> <td> STARTTLS session encryption </td> <td>TLS_README</td> <td>
Postfix 2.2 </td> </tr>

</table>

</blockquote>

<p> Note: IP version 6 support is compiled into Postfix on operating
systems that have IPv6 support. See the IPV6_README file for details.
</p>

<h3>4.4 - Overriding built-in parameter default settings</h3>

<p> All Postfix configuration parameters can be changed by editing
a Postfix configuration file, except for one: the parameter that
specifies the location of Postfix configuration files. In order to
build Postfix with a configuration directory other than /etc/postfix,
use: </p>

<blockquote>
<pre>
% make makefiles CCARGS='-DDEF_CONFIG_DIR=\"/some/where\"'
% make
</pre>
</blockquote>

<p> IMPORTANT: Be sure to get the quotes right. These details matter
a lot. </p>

<p> Parameters whose defaults can be specified in this way are: </p>

<blockquote>

<table border="1">

<tr><th> Macro name </th> <th>default value for</th>  <th>typical
default</th> </tr>

<tr> <td>DEF_COMMAND_DIR</td> <td>command_directory</td>
<td>/usr/sbin</td> </tr>

<tr> <td>DEF_CONFIG_DIR</td> <td>config_directory</td>
<td>/etc/postfix</td> </tr>

<tr> <td>DEF_DAEMON_DIR</td> <td>daemon_directory</td>
<td>/usr/libexec/postfix</td> </tr>

<tr> <td>DEF_DATA_DIR</td> <td>data_directory</td>
<td>/var/db/postfix</td> </tr>

<tr> <td>DEF_MAILQ_PATH</td> <td>mailq_path</td> <td>/usr/bin/mailq</td>
</tr>

<tr> <td>DEF_HTML_DIR</td> <td>html_directory</td>
<td>no</td> </tr>

<tr> <td>DEF_MANPAGE_DIR</td> <td>manpage_directory</td>
<td>/usr/local/man</td> </tr>

<tr> <td>DEF_NEWALIAS_PATH</td> <td>newaliases_path</td>
<td>/usr/bin/newaliases</td> </tr>

<tr> <td>DEF_QUEUE_DIR</td> <td>queue_directory</td>
<td>/var/spool/postfix</td> </tr>

<tr> <td>DEF_README_DIR</td> <td>readme_directory</td>
<td>no</td> </tr>

<tr> <td>DEF_SENDMAIL_PATH</td> <td>sendmail_path</td>
<td>/usr/sbin/sendmail</td> </tr>

</table>

</blockquote>

<p> Note: the data_directory parameter (for caches and pseudo-random
numbers) was introduced with Postfix version 2.5. </p>

<h3>4.5 - Support for thousands of processes</h3>

<p> The number of connections that Postfix can manage simultaneously
is limited by the number of processes that it can run.  This number
in turn is limited by the number of files and sockets that a single
process can open. For example, the Postfix queue manager has a
separate connection to each delivery process, and the anvil(8)
server has one connection per smtpd(8) process. </p>

<p> Postfix version 2.4 and later have no built-in limits on the
number of open files or sockets, when compiled on systems that
support one of the following: </p>

<ul>

<li> BSD kqueue(2) (FreeBSD 4.1, NetBSD 2.0, OpenBSD 2.9),

<li> Solaris 8 /dev/poll,

<li> Linux 2.6 epoll(4).

</ul>


<p> With other Postfix versions or operating systems, the number
of file descriptors per process is limited by the value of the
FD_SETSIZE macro. If you expect to run more than 1000 mail delivery
processes, you may need to override the definition of the FD_SETSIZE
macro to make select() work correctly: </p>

<blockquote>
<pre>
% make makefiles CCARGS=-DFD_SETSIZE=2048
</pre>
</blockquote>

<p> Warning: the above has no effect on some Linux versions.
Apparently, on these systems the FD_SETSIZE value can be changed
only by using undocumented interfaces. Currently, that means
including &lt;bits/types.h&gt; directly (which is not allowed) and
overriding the __FD_SETSIZE macro. Beware, undocumented interfaces
can change at any time and without warning. </p>

<p> But wait, there is more: none of this will work unless the
operating system is configured to handle thousands of connections.
See the TUNING_README guide for examples of how to increase the
number of open sockets or files. </p>

<h3>4.6 - Compiling Postfix, at last</h3>

<p> If the command </p>

<blockquote>
<pre>
% make
</pre>
</blockquote>

<p> is successful, then you can proceed to <a href="#install">install</a>
Postfix (section 6).

<p> If the command produces compiler error messages, it may be time
to search the web or to ask the postfix-users@postfix.org mailing
list, but be sure to search the mailing list archives first. Some
mailing list archives are linked from http://www.postfix.org/. </p>

<h2> <a name="5">5 - Porting Postfix to an unsupported system</a> </h2>

<p> Each system type that Postfix knows is identified by a unique
name. Examples:  SUNOS5, FREEBSD4, and so on.  When porting Postfix
to a new system, the first step is to choose a SYSTEMTYPE name for
the new system. You must use a name that includes at least the
major version of the operating system (such as SUNOS4 or LINUX2),
so that different releases of the same system can be supported
without confusion.  </p>

<p> Add a case statement to the "makedefs" shell script in the
source code top-level directory that recognizes the new system
reliably, and that emits the right system-specific information.
Be sure to make the code robust against user PATH settings; if the
system offers multiple UNIX flavors (e.g. BSD and SYSV) be sure to
build for the native flavor, instead of the emulated one. </p>

<p> Add an "#ifdef SYSTEMTYPE" section to the central util/sys_defs.h
include file.  You may have to invent new feature macro names.
Please choose sensible feature macro names such as HAS_DBM or
FIONREAD_IN_SYS_FILIO_H.

<p> I strongly recommend against using "#ifdef SYSTEMTYPE" in
individual source files.  While this may look like the quickest
solution, it will create a mess when newer versions of the same
SYSTEMTYPE need to be supported.  You're likely to end up placing
"#ifdef" sections all over the source code again.  </p>

<h2><a name="install">6 - Installing the software after successful
compilation</a></h2>

<p> This text describes how to install Postfix from source code.
See the PACKAGE_README file if you are building a package for
distribution to other systems. </p>

<h3>6.1 - Save existing Sendmail binaries</h3>

<p> <a name="save">IMPORTANT</a>: if you are REPLACING an existing
Sendmail installation with Postfix, you may need to keep the old
sendmail program running for some time in order to flush the mail
queue. </p>

<ul>

<li> <p> Some systems implement a mail switch mechanism where
different MTAs (Postfix, Sendmail, etc.) can be installed at the
same time, while only one of them is actually being used. Examples
of such switching mechanisms are the FreeBSD mailwrapper(8) or the
Linux mail switch.  In this case you should try to "flip" the switch
to "Postfix" before installing Postfix. </p>

<li> <p> If your system has no mail switch mechanism, execute the
following commands (your sendmail, newaliases and mailq programs
may be in a different place): </p>

<pre>
# mv /usr/sbin/sendmail /usr/sbin/sendmail.OFF
# mv /usr/bin/newaliases /usr/bin/newaliases.OFF
# mv /usr/bin/mailq /usr/bin/mailq.OFF
# chmod 755 /usr/sbin/sendmail.OFF /usr/bin/newaliases.OFF \
    /usr/bin/mailq.OFF
</pre>

</ul>

<h3>6.2 - Create account and groups</h3>

<p> Before you install Postfix for the first time you need to
create an account and a group:</p>

<ul>

<li> <p> Create a user account "postfix" with a user id and group
id that are not used by any other user account.  Preferably, this
is an account that no-one can log into.  The account does not need
an executable login shell, and needs no existing home directory.
My password and group file entries look like this: </p>

<blockquote>
<pre>
/etc/passwd:
    postfix:*:12345:12345:postfix:/no/where:/no/shell

/etc/group:
    postfix:*:12345:
</pre>
</blockquote>

<p> Note: there should be no whitespace before "postfix:". </p>

<li> <p> Create a group "postdrop" with a group id that is not used
by any other user account. Not even by the postfix user account.
My group file entry looks like:

<blockquote>
<pre>
/etc/group:
    postdrop:*:54321:
</pre>
</blockquote>

<p> Note: there should be no whitespace before "postdrop:". </p>

</ul>

<h3>6.3 - Install Postfix</h3>

<p> To install or upgrade Postfix from compiled source code, run
one of the following commands as the super-user:</p>

<blockquote>
<pre>
# make install       (interactive version, first time install)

# make upgrade       (non-interactive version, for upgrades)
</pre>
</blockquote>

<ul>

<li> <p> The interactive version ("make install") asks for pathnames
for Postfix data and program files, and stores your preferences in
the main.cf file. <b> If you don't want Postfix to overwrite
non-Postfix "sendmail", "mailq" and "newaliases" files, specify
pathnames that end in ".postfix"</b>. </p>

<li> <p> The non-interactive version ("make upgrade") needs the
/etc/postfix/main.cf file from a previous installation. If the file
does not exist, use interactive installation ("make install")
instead. </p>

</ul>

<h3>6.4 - Configure Postfix</h3>

<p> Proceed to the section on how you wish to run Postfix on
your particular machine: </p>

<ul>

<li> <p> <a href="#send_only">Send</a> mail only, without changing
an existing Sendmail installation (section 7). </p>

<li> <p> <a href="#send_receive">Send and receive</a> mail via a
virtual host interface, still without any change to an existing
Sendmail installation (section 8). </p>

<li> <p> Run Postfix <a href="#replace">instead of</a> Sendmail
(section 9). </p>

</ul>

<h2><a name="send_only">7 - Configuring Postfix to send mail
only</a></h2>

<p> If you are going to use Postfix to send mail only, there is no
need to change your existing sendmail setup. Instead, set up your
mail user agent so that it calls the Postfix sendmail program
directly. </p>

<p> Follow the instructions in the "<a href="#mandatory">Mandatory
configuration file edits</a>" in section 10, and review the "<a
href="#hamlet">To chroot or not to chroot</a>" text in section
11. </p>

<p> You MUST comment out the "smtp inet" entry in /etc/postfix/master.cf,
in order to avoid conflicts with the real sendmail. Put a "#"
character in front of the line that defines the smtpd service: </p>

<blockquote>
<pre>
/etc/postfix/master.cf:
    #smtp      inet  n       -       n       -       -       smtpd
</pre>
</blockquote>

<p> Start the Postfix system: </p>

<blockquote>
<pre>
# postfix start
</pre>
</blockquote>

<p> or, if you feel nostalgic, use the Postfix sendmail command: </p>

<blockquote>
<pre>
# sendmail -bd -qwhatever
</pre>
</blockquote>

<p> and watch your maillog file for any error messages. The pathname
is /var/log/maillog, /var/log/mail, /var/log/syslog, or something
else. Typically, the pathname is defined in the /etc/syslog.conf
file. </p>

<blockquote>
<pre>
% egrep '(reject|warning|error|fatal|panic):' /some/log/file
</pre>
</blockquote>

<p> Note: the most important error message is logged first. Later
messages are not as useful. </p>

<p> In order to inspect the mail queue, use one of the following
commands: </p>

<blockquote>
<pre>
% mailq

% sendmail -bp

% postqueue -p
</pre>
</blockquote>

<p> See also the "<a href="#care">Care and feeding</a>" section 12
below.  </p>

<h2><a name="send_receive">8 - Configuring Postfix to send and
receive mail via virtual interface</a></h2>

<p> Alternatively, you can use the Postfix system to send AND
receive mail while leaving your Sendmail setup intact, by running
Postfix on a virtual interface address.  Simply configure your mail
user agent to directly invoke the Postfix sendmail program.  </p>

<p> To create a virtual network interface address, study your
system ifconfig manual page. The command syntax could be any
of: </p>

<blockquote>
<pre>
# <b>ifconfig le0:1 &lt;address&gt; netmask &lt;mask&gt; up</b>
# <b>ifconfig en0 alias &lt;address&gt; netmask 255.255.255.255</b>
</pre>
</blockquote>

<p> In the /etc/postfix/main.cf file, I would specify </p>

<blockquote>
<pre>
/etc/postfix/main.cf:
    myhostname = virtual.host.tld
    inet_interfaces = $myhostname
    mydestination = $myhostname
</pre>
</blockquote>

<p> Follow the instructions in the "<a href="#mandatory">Mandatory
configuration file edits</a>" in section 10, and review the "<a
name="#hamlet">To chroot or not to chroot</a>" text in section
11. </p>

<p> Start the Postfix system: </p>

<blockquote>
<pre>
# postfix start
</pre>
</blockquote>

<p> or, if you feel nostalgic, use the Postfix sendmail command: </p>

<blockquote>
<pre>
# sendmail -bd -qwhatever
</pre>
</blockquote>

<p> and watch your maillog file for any error messages. The pathname
is /var/log/maillog, /var/log/mail, /var/log/syslog, or something
else. Typically, the pathname is defined in the /etc/syslog.conf
file. </p>

<blockquote>
<pre>
% egrep '(reject|warning|error|fatal|panic):' /some/log/file
</pre>
</blockquote>

<p> Note: the most important error message is logged first. Later
messages are not as useful. </p>

<p> In order to inspect the mail queue, use one of the following
commands: </p>

<blockquote>
<pre>
% mailq

% sendmail -bp

% postqueue -p
</pre>
</blockquote>

<p> See also the "<a href="#care">Care and feeding</a>" section 12
below.  </p>

<h2><a name="replace">9 - Running Postfix instead of Sendmail</a></h2>

<p> Prior to installing Postfix you should <a href="#save">save</a>
any existing sendmail program files as described in section 6.  Be
sure to keep the old sendmail running for at least a couple days
to flush any unsent mail. To do so, stop the sendmail daemon and
restart it as: </p>

<blockquote>
<pre>
# /usr/sbin/sendmail.OFF -q
</pre>
</blockquote>

<p> Note: this is old sendmail syntax. Newer versions use separate
processes for mail submission and for running the queue. </p>

<p> After you have visited the "<a href="#mandatory">Mandatory
configuration file edits</a>" section below, you can start the
Postfix system with: </p>

<blockquote>
<pre>
# postfix start
</pre>
</blockquote>

<p> or, if you feel nostalgic, use the Postfix sendmail command: </p>

<blockquote>
<pre>
# sendmail -bd -qwhatever
</pre>
</blockquote>

<p> and watch your maillog file for any error messages. The pathname
is /var/log/maillog, /var/log/mail, /var/log/syslog, or something
else. Typically, the pathname is defined in the /etc/syslog.conf
file. </p>

<blockquote>
<pre>
% egrep '(reject|warning|error|fatal|panic):' /some/log/file
</pre>
</blockquote>

<p> Note: the most important error message is logged first. Later
messages are not as useful. </p>

<p> In order to inspect the mail queue, use one of the following
commands: </p>

<blockquote>
<pre>
% mailq

% sendmail -bp

% postqueue -p
</pre>
</blockquote>

<p> See also the "<a href="#care">Care and feeding</a>" section 12
below.  </p>

<h2><a name="mandatory">10 - Mandatory configuration file edits</a></h2>

<p> Note: the material covered in this section is covered in more
detail in the BASIC_CONFIGURATION_README document. The information
presented below is targeted at experienced system administrators.
</p>

<h3>10.1 - Postfix configuration files</h3>

<p> By default, Postfix configuration files are in /etc/postfix.
The two most important files are main.cf and master.cf; these files
must be owned by root.  Giving someone else write permission to
main.cf or master.cf (or to their parent directories) means giving
root privileges to that person. </p>

<p> In /etc/postfix/main.cf, you will have to set up a minimal number
of configuration parameters.  Postfix configuration parameters
resemble shell variables, with two important differences: the first
one is that Postfix does not know about quotes like the UNIX shell
does.</p>

<p> You specify a configuration parameter as: </p>

<blockquote>
<pre>
/etc/postfix/main.cf:
    parameter = value
</pre>
</blockquote>

<p> and you use it by putting a "$" character in front of its name: </p>

<blockquote>
<pre>
/etc/postfix/main.cf:
    other_parameter = $parameter
</pre>
</blockquote>

<p> You can use $parameter before it is given a value (that is the
second main difference with UNIX shell variables). The Postfix
configuration language uses lazy evaluation, and does not look at
a parameter value until it is needed at runtime.  </p>

<p> Whenever you make a change to the main.cf or master.cf file,
execute the following command in order to refresh a running mail
system: </p>

<blockquote>
<pre>
# postfix reload
</pre>
</blockquote>

<h3>10.2 - Default domain for unqualified addresses</h3>

<p> First of all, you must specify what domain will be appended to an
unqualified address (i.e. an address without @domain.tld). The
"myorigin" parameter defaults to the local hostname, but that is
probably OK only for very small sites.  </p>

<p> Some examples (use only one): </p>

<blockquote>
<pre>
/etc/postfix/main.cf:
    myorigin = $myhostname    (send mail as "user@$myhostname")
    myorigin = $mydomain      (send mail as "user@$mydomain")
</pre>
</blockquote>

<h3>10.3 - What domains to receive locally</h3>

<p> Next you need to specify what mail addresses Postfix should deliver
locally. </p>

<p> Some examples (use only one): </p>

<blockquote>
<pre>
/etc/postfix/main.cf:
    mydestination = $myhostname, localhost.$mydomain, localhost
    mydestination = $myhostname, localhost.$mydomain, localhost, $mydomain
    mydestination = $myhostname
</pre>
</blockquote>

<p>The first example is appropriate for a workstation, the second
is appropriate for the mailserver for an entire domain. The third
example should be used when running on a virtual host interface.</p>

<h3>10.4 - Proxy/NAT interface addresses </h3>

<p> The proxy_interfaces parameter specifies all network addresses
that Postfix receives mail on by way of a proxy or network address
translation unit. You may specify symbolic hostnames instead of
network addresses. </p>

<p> IMPORTANT: You must specify your proxy/NAT external addresses
when your system is a backup MX host for other domains, otherwise
mail delivery loops will happen when the primary MX host is down.
</p>

<p> Example: host behind NAT box running a backup MX host. </p>

<blockquote>
<pre>
/etc/postfix/main.cf:
    proxy_interfaces = 1.2.3.4 (the proxy/NAT external network address)
</pre>
</blockquote>

<h3>10.5 - What local clients to relay mail from </h3>

<p> If your machine is on an open network then you must specify
what client IP addresses are authorized to relay their mail through
your machine into the Internet.  The default setting includes all
subnetworks that the machine is attached to. This may give relay
permission to too many clients.  My own settings are: </p>

<blockquote>
<pre>
/etc/postfix/main.cf:
    mynetworks = 168.100.189.0/28, 127.0.0.0/8
</pre>
</blockquote>

<h3>10.6 - What relay destinations to accept from strangers </h3>

<p> If your machine is on an open network then you must also specify
whether Postfix will forward mail from strangers.  The default
setting will forward mail to all domains (and subdomains of) what
is listed in $mydestination.  This may give relay permission for
too many destinations.  Recommended settings (use only one): </p>

<blockquote>
<pre>
/etc/postfix/main.cf:
    relay_domains =            (do not forward mail from strangers)
    relay_domains = $mydomain  (my domain and subdomains)
    relay_domains = $mydomain, other.domain.tld, ...
</pre>
</blockquote>

<h3>10.7 - Optional: configure a smart host for remote delivery</h3>

<p> If you're behind a firewall, you should set up a relayhost.  If
you can, specify the organizational domain name so that Postfix
can use DNS lookups, and so that it can fall back to a secondary
MX host when the primary MX host is down. Otherwise just specify
a hard-coded hostname.  </p>

<p> Some examples (use only one): </p>

<blockquote>
<pre>
/etc/postfix/main.cf:
    relayhost = $mydomain
    relayhost = [mail.$mydomain]
</pre>
</blockquote>

<p> The form enclosed with <tt>[]</tt> eliminates DNS MX lookups. </p>

<p> By default, the SMTP client will do DNS lookups even when you
specify a relay host. If your machine has no access to a DNS server,
turn off SMTP client DNS lookups like this: </p>

<blockquote>
<pre>
/etc/postfix/main.cf:
    disable_dns_lookups = yes
</pre>
</blockquote>

<p> The STANDARD_CONFIGURATION_README file has more hints and tips for
firewalled and/or dial-up networks. </p>

<h3>10.8 - Create the aliases database</h3>

<p> Postfix uses a Sendmail-compatible aliases(5) table to redirect
mail for local(8) recipients.  Typically, this information is kept
in two files: in a text file /etc/aliases and in an indexed file
/etc/aliases.db.  The command "postconf alias_maps" will tell you
the exact location of the text file.  </p>

<p> First, be sure to update the text file with aliases for root,
postmaster and "postfix" that forward mail to a real person.  Postfix
has a sample aliases file /etc/postfix/aliases that you can adapt
to local conditions.  </p>

<blockquote>
<pre>
/etc/aliases:
    root: you
    postmaster: root
    postfix: root
    bin: root
    <i>etcetera...</i>
</pre>
</blockquote>

<p> Note: there should be no whitespace before the ":". </p>

<p> Finally, build the indexed aliases file with one of the
following commands: </p>

<blockquote>
<pre>
# newaliases
# sendmail -bi
</pre>
</blockquote>

<h2><a name="hamlet">11 - To chroot or not to chroot</a></h2>

<p> Postfix daemon processes can be configured (via master.cf) to
run in a chroot jail.  The processes run at a fixed low privilege
and with access only to the Postfix queue directories (/var/spool/postfix).
This provides a significant barrier against intrusion. The barrier
is not impenetrable, but every little bit helps. </p>

<p> With the exception of Postfix daemons that deliver mail locally
and/or that execute non-Postfix commands, every Postfix daemon can
run chrooted. </p>

<p> Sites with high security requirements should consider to chroot
all daemons that talk to the network:  the smtp(8) and smtpd(8)
processes, and perhaps also the lmtp(8) client. The author's own
porcupine.org mail server runs all daemons chrooted that can be
chrooted. </p>

<p> The default /etc/postfix/master.cf file specifies that no
Postfix daemon runs chrooted.  In order to enable chroot operation,
edit the file /etc/postfix/master.cf. Instructions are in the file.
</p>

<p> Note that a chrooted daemon resolves all filenames relative to
the Postfix queue directory (/var/spool/postfix). For successful
use of a chroot jail,  most UNIX systems require you to bring in
some files or device nodes.  The examples/chroot-setup directory
in the source code distribution has a collection of scripts that
help you set up Postfix chroot environments on different operating
systems. </p>

<p> Additionally, you almost certainly need to configure syslogd
so that it listens on a socket inside the Postfix queue directory.
Examples for specific systems: </p>

<dl>

<dt> FreeBSD: </dt>

<dd> <pre>
# mkdir -p /var/spool/postfix/var/run
# syslogd -l /var/spool/postfix/var/run/log
</pre> </dd>

<dt> Linux, OpenBSD: </dt>

<dd> <pre>
# mkdir -p /var/spool/postfix/dev
# syslogd -a /var/spool/postfix/dev/log
</pre> </dd>

</dl>

<h2><a name="care">12 - Care and feeding of the Postfix system</a></h2>

<p> Postfix daemon processes run in the background, and log problems
and normal activity to the syslog daemon. The names of logfiles
are specified in /etc/syslog.conf. At the very least you need
something like:  </p>

<blockquote>
<pre>
/etc/syslog.conf:
    mail.err                                    /dev/console
    mail.debug                                  /var/log/maillog
</pre>
</blockquote>

<p> IMPORTANT: the syslogd will not create files. You must create
them before (re)starting syslogd. </p>

<p> IMPORTANT: on Linux you need to put a "-" character before
the pathname, e.g., -/var/log/maillog, otherwise the syslogd
will use more system resources than Postfix does. </p>

<p> Hopefully, the number of problems will be small, but it is a good
idea to run every night before the syslog files are rotated: </p>

<blockquote>
<pre>
# postfix check
# egrep '(reject|warning|error|fatal|panic):' /some/log/file
</pre>
</blockquote>

<ul>

<li> <p> The first line (postfix check) causes Postfix to report
file permission/ownership discrepancies. </p>

<li> <p> The second line looks for problem reports from the mail
software, and reports how effective the relay and junk mail access
blocks are.  This may produce a lot of output.  You will want to
apply some postprocessing to eliminate uninteresting information.
</p>

</ul>

<p>  The <a href="DEBUG_README.html#logging"> DEBUG_README </a>
document describes the meaning of the "warning" etc. labels in
Postfix logging. </p>

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