Postfix Installation From Source Code

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1 - Purpose of this document

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.

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

  * Send mail only, without changing an existing Sendmail installation.
  * Send and receive mail via a virtual host interface, still without any
    change to an existing Sendmail installation.
  * Run Postfix instead of Sendmail.

Topics covered in this document:

 1. Purpose of this document
 2. Typographical conventions
 3. Documentation
 4. Building on a supported system
 5. Porting Postfix to an unsupported system
 6. Installing the software after successful compilation
 7. Configuring Postfix to send mail only
 8. Configuring Postfix to send and receive mail via virtual interface
 9. Running Postfix instead of Sendmail
10. Mandatory configuration file edits
11. To chroot or not to chroot
12. Care and feeding of the Postfix system

2 - Typographical conventions

In the instructions below, a command written as

    # command

should be executed as the superuser.

A command written as

    $ command

should be executed as an unprivileged user.

3 - Documentation

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.

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 bold font. To
print a README file without backspace characters, use the col(1) command. For
example:

    $ col -bx <file | lpr

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.

    $ export MANPATH; MANPATH="`pwd`/man:$MANPATH"
    $ setenv MANPATH "`pwd`/man:$MANPATH"

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.

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

4 - Building on a supported system

Postfix development happens on FreeBSD and MacOS X, with regular tests on Linux
(Fedora, Ubuntu) and Solaris. Support for other systems relies on feedback from
their users, and may not always be up-to-date.

OpenBSD is partially supported. The libc resolver does not implement the
documented "internal resolver options which are [...] set by changing fields in
the _res structure" (documented in the OpenBSD 5.6 resolver(3) manpage). This
results in too many DNS queries, and false positives for queries that should
fail.

Overview of topics:

  * 4.1 - Getting started
  * 4.2 - What compiler to use
  * 4.3 - Building with Postfix position-independent executables (Postfix >=
    3.0)
  * 4.4 - Building with Postfix dynamically-linked libraries and database
    plugins (Postfix >= 3.0)
  * 4.5 - Building with optional features
  * 4.6 - Overriding built-in parameter default settings
  * 4.7 - Overriding other compile-time features
  * 4.8 - Support for thousands of processes
  * 4.9 - Compiling Postfix, at last

4.1 - Getting started

On Solaris, the "make" command and other development utilities are in /usr/ccs/
bin, so you MUST have /usr/ccs/bin in your command search path. If these files
do not exist, you need to install the development packages first.

If you need to build Postfix for multiple architectures from a single source-
code tree, use the "lndir" command to build a shadow tree with symbolic links
to the source files.

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:

    $ make -f Makefile.init makefiles

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:

    $ make tidy

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

4.2 - What compiler to use

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:

    $ make

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

    $ 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

and so on. In some cases, optimization will be turned off automatically.

4.3 - Building with Postfix position-independent executables (Postfix >= 3.0)

On some systems Postfix can be built with Position-Independent Executables. PIE
is used by the ASLR exploit mitigation technique (ASLR = Address-Space Layout
Randomization):

    $ make makefiles pie=yes ...other arguments...

(Specify "make makefiles pie=no" to explicitly disable Postfix position-
independent executable support).

Postfix PIE support appears to work on Fedora Core 20, Ubuntu 14.04, FreeBSD 9
and 10, and NetBSD 6 (all with the default system compilers).

Whether the "pie=yes" above has any effect depends on the compiler. Some
compilers always produce PIE executables, and some may even complain that the
Postfix build option is redundant.

4.4 - Building with Postfix dynamically-linked libraries and database plugins
(Postfix >= 3.0)

Postfix dynamically-linked library and database plugin support exists for
recent versions of Linux, FreeBSD and MacOS X. Dynamically-linked library
builds may become the default at some point in the future.

Overview of topics:

  * 4.4.1 Turning on Postfix dynamically-linked library support
  * 4.4.2 Turning on Postfix database-plugin support
  * 4.4.3 Customizing Postfix dynamically-linked libraries and database plugins
  * 4.4.4 Tips for distribution maintainers

Note: directories with Postfix dynamically-linked libraries or database plugins
should contain only postfix-related files. Postfix dynamically-linked libraries
and database plugins should not be installed in a "public" system directory
such as /usr/lib or /usr/local/lib. Linking Postfix dynamically-linked library
or database-plugin files into non-Postfix programs is not supported. Postfix
dynamically-linked libraries and database plugins implement a Postfix-internal
API that changes without maintaining compatibility.

4.4.1 Turning on Postfix dynamically-linked library support

Postfix can be built with Postfix dynamically-linked libraries (files typically
named libpostfix-*.so). Postfix dynamically-linked libraries add minor run-time
overhead and result in significantly-smaller Postfix executable files.

Specify "shared=yes" on the "make makefiles" command line to build Postfix with
dynamically-linked library support.

    $ make makefiles shared=yes ...other arguments...
    $ make

(Specify "make makefiles shared=no" to explicitly disable Postfix dynamically-
linked library support).

This installs dynamically-linked libraries in $shlib_directory, typically /usr/
lib/postfix or /usr/local/lib/postfix, with file names libpostfix-name.so,
where the name is a source-code directory name such as "util" or "global".

See section 4.4.3 "Customizing Postfix dynamically-linked libraries and
database plugins" below for how to customize the Postfix dynamically-linked
library location, including support to upgrade a running mail system safely.

4.4.2 Turning on Postfix database-plugin support

Additionally, Postfix can be built to support dynamic loading of Postfix
database clients (database plugins) with the Debian-style dynamicmaps feature.
Postfix 3.0 supports dynamic loading of cdb:, ldap:, lmdb:, mysql:, pcre:,
pgsql:, sdbm:, and sqlite: database clients. Dynamic loading is useful when you
distribute or install pre-compiled Postfix packages.

Specify "dynamicmaps=yes" on the "make makefiles" command line to build Postfix
with support to dynamically load Postfix database clients with the Debian-style
dynamicmaps feature.

    $ make makefiles dynamicmaps=yes ...other arguments...
    $ make

(Specify "make makefiles dynamicmaps=no" to explicitly disable Postfix
database-plugin support).

This implicitly enables dynamically-linked library support, installs the
configuration file dynamicmaps.cf in $meta_directory (usually, /etc/postfix or
/usr/local/etc/postfix), and installs database plugins in $shlib_directory (see
above). Database plugins are named postfix-type.so where the type is a database
type such as "cdb" or "ldap".

    NOTE: The Postfix 3.0 build procedure expects that you specify database
    library dependencies with variables named AUXLIBS_CDB, AUXLIBS_LDAP, etc.
    With Postfix 3.0 and later, the old AUXLIBS variable still supports
    building a statically-loaded database client, but only the new AUXLIBS_CDB
    etc. variables support building a dynamically-loaded or statically-loaded
    CDB etc. database client. See CDB_README, LDAP_README, etc. for details.

    Failure to follow this advice will defeat the purpose of dynamic database
    client loading. Every Postfix executable file will have database library
    dependencies. And that was exactly what dynamic database client loading was
    meant to avoid.

See the next section for how to customize the location and version of Postfix
database plugins and the location of the file dynamicmaps.cf.

4.4.3 Customizing Postfix dynamically-linked libraries and database plugins

Customizing build-time and run-time options for Postfix dynamically-linked
libraries and database plugins

The build-time environment variables SHLIB_CFLAGS, SHLIB_RPATH, and
SHLIB_SUFFIX provide control over how Postfix libraries and plugins are
compiled, linked, and named.

    $ make makefiles SHLIB_CFLAGS=flags SHLIB_RPATH=rpath SHLIB_SUFFIX=suffix
    ...other arguments...
    $ make

See section 4.7 "Overriding other compile-time features" below for details.

Customizing the location of Postfix dynamically-linked libraries and database
plugins

As a reminder, the directories with Postfix dynamically-linked libraries or
database plugins should contain only Postfix-related files. Linking these files
into other programs is not supported.

To override the default location of Postfix dynamically-linked libraries and
database plugins specify, for example:

    $ make makefiles shared=yes shlib_directory=/usr/local/lib/postfix ...

If you intend to upgrade Postfix without stopping the mail system, then you
should append the Postfix release version to the shlib_directory pathname, to
eliminate the possibility that programs will link with dynamically-linked
libraries or database plugins from the wrong Postfix version. For example:

    $ make makefiles shared=yes \
        shlib_directory=/usr/local/lib/postfix/MAIL_VERSION ...

The command "make makefiles name=value..." will replace the string MAIL_VERSION
at the end of a configuration parameter value with the Postfix release version.
Do not try to specify something like $mail_version on this command line. This
produces inconsistent results with different versions of the make(1) command.

You can change the shlib_directory setting after Postfix is built, with "make
install" or "make upgrade". However, you may have to run ldconfig if you change
shlib_directory after Postfix is built (the symptom is that Postfix programs
fail because the run-time linker cannot find the files libpostfix-*.so). No
ldconfig command is needed if you keep the files libpostfix-*.so in the
compiled-in default $shlib_directory location.

    # make upgrade shlib_directory=/usr/local/lib/postfix ...
    # make install shlib_directory=/usr/local/lib/postfix ...

To append the Postfix release version to the pathname if you intend to upgrade
Postfix without stopping the mail system:

    # make upgrade shlib_directory=/usr/local/lib/postfix/MAIL_VERSION ...
    # make install shlib_directory=/usr/local/lib/postfix/MAIL_VERSION ...

See also the comments above for appending MAIL_VERSION with the "make
makefiles" command.

Customizing the location of dynamicmaps.cf and other files

The meta_directory parameter has the same default setting as the
config_directory parameter, typically /etc/postfix or /usr/local/etc/postfix.

You can override the default meta_directory location at compile time or after
Postfix is built. To override the default location at compile time specify, for
example:

    % make makefiles meta_directory=/usr/libexec/postfix ...

Here is a tip if you want to make a pathname dependent on the Postfix release
version: the command "make makefiles name=value..." will replace the string
MAIL_VERSION at the end of a configuration parameter value with the Postfix
release version. Do not try to specify something like $mail_version on this
command line. This produces inconsistent results with different versions of the
make(1) command.

You can override the meta_directory setting after Postfix is built, with "make
install" or "make upgrade".

    # make upgrade meta_directory=/usr/libexec/postfix ...
    # make install meta_directory=/usr/libexec/postfix ...

As with the command "make makefiles", the command "make install/upgrade
name=value..." will replace the string MAIL_VERSION at the end of a
configuration parameter value with the Postfix release version. Do not try to
specify something like $mail_version on this command line. This produces
inconsistent results with different versions of the make(1) command.

4.4.4 Tips for distribution maintainers

  * The shlib_directory parameter setting also provides the default directory
    for database plugin files with a relative pathname in the file
    dynamicmaps.cf.

  * The meta_directory parameter specifies the location of the files
    dynamicmaps.cf, postfix-files, and some multi-instance template files. The
    meta_directory parameter has the same default value as the config_directory
    parameter (typically, /etc/postfix or /usr/local/etc/postfix). For
    backwards compatibility with Postfix 2.6 .. 2.11, specify "meta_directory =
    $daemon_directory" in main.cf before installing or upgrading Postfix, or
    specify "meta_directory = /path/name" on the "make makefiles", "make
    install" or "make upgrade" command line.

  * The configuration file dynamicmaps.cf will automatically include files
    under the directory dynamicmaps.cf.d, just like the configuration file
    postfix-files will automatically include files under the directory postfix-
    files.d. Thanks to this, you can install or deinstall a database plugin
    package without having to edit postfix-files or dynamicmaps.cf. Instead,
    you give that plugin its own configuration files under dynamicmaps.cf.d and
    postfix-files.d, and you add or remove those configuration files along with
    the database plugin dynamically-linked object.

  * Each configuration file under the directory dynamicmaps.cf.d must have the
    same format as the configuration file dynamicmaps.cf. There is no
    requirement that these configuration file *names* have a specific format.

  * Each configuration file under the directory postfix-files.d must have the
    same format as the configuration file postfix-files. There is no
    requirement that these configuration file *names* have a specific format.

4.5 - Building with optional features

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 optional features:

                                                                   
    |Optional feature                  |Document      |Availability|
    |                                  |              |            |
    |Berkeley DB database              |DB_README     |Postfix 1.0 |
    |                                  |              |            |
    |LMDB database                     |LMDB_README   |Postfix 2.11|
    |                                  |              |            |
    |LDAP database                     |LDAP_README   |Postfix 1.0 |
    |                                  |              |            |
    |MongoDB database                  |MONGODB_README|Postfix 3.9 |
    |                                  |              |            |
    |MySQL database                    |MYSQL_README  |Postfix 1.0 |
    |                                  |              |            |
    |Perl compatible regular expression|PCRE_README   |Postfix 1.0 |
    |                                  |              |            |
    |PostgreSQL database               |PGSQL_README  |Postfix 2.0 |
    |                                  |              |            |
    |SASL authentication               |SASL_README   |Postfix 1.0 |
    |                                  |              |            |
    |SQLite database                   |SQLITE_README |Postfix 2.8 |
    |                                  |              |            |
    |STARTTLS session encryption       |TLS_README    |Postfix 2.2 |
    |                                  |              |            |

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

4.6 - Overriding built-in parameter default settings

4.6.1 - Postfix 3.0 and later

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:

    $ make makefiles config_directory=/some/where ...other arguments...
    $ make

The command "make makefiles name=value ..." will replace the string
MAIL_VERSION at the end of a configuration parameter value with the Postfix
release version. Do not try to specify something like $mail_version on this
command line. This produces inconsistent results with different versions of the
make(1) command.

Parameters whose defaults can be specified in this way are listed below. See
the postconf(5) manpage for a description (command: "nroff -man man/man5/
postconf.5 | less").

                                               
    |parameter name       |typical default     |
    |                     |                    |
    |command_directory    |/usr/sbin           |
    |                     |                    |
    |config_directory     |/etc/postfix        |
    |                     |                    |
    |default_database_type|hash                |
    |                     |                    |
    |daemon_directory     |/usr/libexec/postfix|
    |                     |                    |
    |data_directory       |/var/lib/postfix    |
    |                     |                    |
    |html_directory       |no                  |
    |                     |                    |
    |mail_spool_directory |/var/mail           |
    |                     |                    |
    |mailq_path           |/usr/bin/mailq      |
    |                     |                    |
    |manpage_directory    |/usr/local/man      |
    |                     |                    |
    |meta_directory       |/etc/postfix        |
    |                     |                    |
    |newaliases_path      |/usr/bin/newaliases |
    |                     |                    |
    |openssl_path         |openssl             |
    |                     |                    |
    |queue_directory      |/var/spool/postfix  |
    |                     |                    |
    |readme_directory     |no                  |
    |                     |                    |
    |sendmail_path        |/usr/sbin/sendmail  |
    |                     |                    |
    |shlib_directory      |/usr/lib/postfix    |
    |                     |                    |

4.6.2 - All Postfix versions

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:

    $ make makefiles CCARGS="-DDEF_CONFIG_DIR=\\\"/some/where\\\""
    $ make

IMPORTANT: Be sure to get the quotes right. These details matter a lot.

Parameters whose defaults can be specified in this way are listed below. See
the postconf(5) manpage for a description (command: "nroff -man man/man5/
postconf.5 | less").

                                                                 
    |Macro name       |default value for    |typical default     |
    |                 |                     |                    |
    |DEF_COMMAND_DIR  |command_directory    |/usr/sbin           |
    |                 |                     |                    |
    |DEF_CONFIG_DIR   |config_directory     |/etc/postfix        |
    |                 |                     |                    |
    |DEF_DB_TYPE      |default_database_type|hash                |
    |                 |                     |                    |
    |DEF_DAEMON_DIR   |daemon_directory     |/usr/libexec/postfix|
    |                 |                     |                    |
    |DEF_DATA_DIR     |data_directory       |/var/lib/postfix    |
    |                 |                     |                    |
    |DEF_MAILQ_PATH   |mailq_path           |/usr/bin/mailq      |
    |                 |                     |                    |
    |DEF_HTML_DIR     |html_directory       |no                  |
    |                 |                     |                    |
    |DEF_MANPAGE_DIR  |manpage_directory    |/usr/local/man      |
    |                 |                     |                    |
    |DEF_NEWALIAS_PATH|newaliases_path      |/usr/bin/newaliases |
    |                 |                     |                    |
    |DEF_QUEUE_DIR    |queue_directory      |/var/spool/postfix  |
    |                 |                     |                    |
    |DEF_README_DIR   |readme_directory     |no                  |
    |                 |                     |                    |
    |DEF_SENDMAIL_PATH|sendmail_path        |/usr/sbin/sendmail  |
    |                 |                     |                    |

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

4.7 - Overriding other compile-time features

The general method to override Postfix compile-time features is as follows:

    $ make makefiles name=value name=value...
    $ make

The following is an extensive list of names and values.

                                                                              
|Name/Value                     |Description                                  |
|                               |                                             |
|                               |Specifies one or more non-default object     |
|                               |libraries. Postfix 3.0 and later specify some|
|                               |of their database library dependencies with  |
|AUXLIBS="object_library..."    |AUXLIBS_CDB, AUXLIBS_LDAP, AUXLIBS_LMDB,     |
|                               |AUXLIBS_MYSQL, AUXLIBS_PCRE, AUXLIBS_PGSQL,  |
|                               |AUXLIBS_SDBM, and AUXLIBS_SQLITE,            |
|                               |respectively.                                |
|                               |                                             |
|CC=compiler_command            |Specifies a non-default compiler. On many    |
|                               |systems, the default is gcc.                 |
|                               |                                             |
|                               |Specifies non-default compiler arguments, for|
|CCARGS="compiler_arguments..." |example, a non-default include directory. The|
|                               |following directives turn off Postfix        |
|                               |features at compile time:                    |
|                               |                                             |
||                              |Do not build with Berkeley DB support. By    |
||                              |default, Berkeley DB support is compiled in  |
||-DNO_DB                       |on platforms that are known to support this  |
||                              |feature. If you override this, then you      |
||                              |probably should also override DEF_DB_TYPE as |
||                              |described in section 4.6.                    |
||                              |                                             |
||-DNO_DNSSEC                   |Do not build with DNSSEC support, even if the|
||                              |resolver library appears to support it.      |
||                              |                                             |
||                              |Do not build with Solaris /dev/poll support. |
||-DNO_DEVPOLL                  |By default, /dev/poll support is compiled in |
||                              |on Solaris versions that are known to support|
||                              |this feature.                                |
||                              |                                             |
||                              |Do not build with Linux EPOLL support. By    |
||-DNO_EPOLL                    |default, EPOLL support is compiled in on     |
||                              |platforms that are known to support this     |
||                              |feature.                                     |
||                              |                                             |
||                              |Do not build with EAI (SMTPUTF8) support. By |
||-DNO_EAI                      |default, EAI support is compiled in when the |
||                              |"icuuc" library and header files are found.  |
||                              |                                             |
||                              |Do not require support for C99 "inline"      |
||                              |functions. Instead, implement argument       |
||-DNO_INLINE                   |typechecks for non-printf/scanf-like         |
||                              |functions with ternary operators and         |
||                              |unreachable code.                            |
||                              |                                             |
||                              |Do not build with IPv6 support. By default,  |
||                              |IPv6 support is compiled in on platforms that|
||                              |are known to have IPv6 support. Note: this   |
||-DNO_IPV6                     |directive is for debugging and testing only. |
||                              |It is not guaranteed to work on all          |
||                              |platforms. If you don't want IPv6 support,   |
||                              |set "inet_protocols = ipv4" in main.cf.      |
||                              |                                             |
||                              |Do not build with FreeBSD / NetBSD / OpenBSD |
||-DNO_KQUEUE                   |/ MacOSX KQUEUE support. By default, KQUEUE  |
||                              |support is compiled in on platforms that are |
||                              |known to support it.                         |
||                              |                                             |
||                              |Do not build with NIS or NISPLUS support. NIS|
||-DNO_NIS                      |is not available on some recent Linux        |
||                              |distributions.                               |
||                              |                                             |
||                              |Do not build with NISPLUS support. NISPLUS is|
||-DNO_NISPLUS                  |not available on some recent Solaris         |
||                              |distributions.                               |
||                              |                                             |
||                              |Do not build with PCRE support. By default,  |
||-DNO_PCRE                     |PCRE support is compiled in when the pcre-   |
||                              |config utility is installed.                 |
||                              |                                             |
||                              |Disable support for POSIX getpwnam_r/        |
||-DNO_POSIX_GETPW_R            |getpwuid_r. By default Postfix uses these    |
||                              |where they are known to be available.        |
||                              |                                             |
||-DNO_RES_NCALLS               |Do not build with the threadsafe resolver(5) |
||                              |API (res_ninit() etc.).                      |
||                              |                                             |
||                              |Use setjmp()/longjmp() instead of sigsetjmp  |
||-DNO_SIGSETJMP                |()/siglongjmp(). By default, Postfix uses    |
||                              |sigsetjmp()/siglongjmp() when they are known |
||                              |to be available.                             |
||                              |                                             |
||                              |Use sprintf() instead of snprintf(). By      |
||-DNO_SNPRINTF                 |default, Postfix uses snprintf() except on   |
||                              |ancient systems.                             |
||                              |                                             |
|                               |Specifies a non-default compiler debugging   |
|DEBUG=debug_level              |level. The default is "-g". Specify DEBUG= to|
|                               |turn off debugging.                          |
|                               |                                             |
|                               |Specifies a non-default optimization level.  |
|OPT=optimization_level         |The default is "-O". Specify OPT= to turn off|
|                               |optimization.                                |
|                               |                                             |
|                               |Specifies options for the postfix-install    |
|POSTFIX_INSTALL_OPTS=-option...|command, separated by whitespace. Currently, |
|                               |the only supported option is "-keep-build-   |
|                               |mtime".                                      |
|                               |                                             |
|                               |Specifies non-default compiler options for   |
|SHLIB_CFLAGS=flags             |building Postfix dynamically-linked libraries|
|                               |and database plugins. The typical default is |
|                               |"-fPIC".                                     |
|                               |                                             |
|                               |Specifies a non-default runpath for Postfix  |
|SHLIB_RPATH=rpath              |dynamically-linked libraries. The typical    |
|                               |default is "'-Wl,-rpath,${SHLIB_DIR}'".      |
|                               |                                             |
|                               |Specifies a non-default suffix for Postfix   |
|SHLIB_SUFFIX=suffix            |dynamically-linked libraries and database    |
|                               |plugins. The typical default is ".so".       |
|                               |                                             |
|                               |Specifies non-default compiler warning       |
|WARN="warning_flags..."        |options for use when "make" is invoked in a  |
|                               |source subdirectory only.                    |
|                               |                                             |

4.8 - Support for thousands of processes

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.

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:

  * BSD kqueue(2) (FreeBSD 4.1, NetBSD 2.0, OpenBSD 2.9),
  * Solaris 8 /dev/poll,
  * Linux 2.6 epoll(4).

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:

    $ make makefiles CCARGS=-DFD_SETSIZE=2048

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 <bits/types.h> directly (which is
not allowed) and overriding the __FD_SETSIZE macro. Beware, undocumented
interfaces can change at any time and without warning.

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.

4.9 - Compiling Postfix, at last

If the command

    $ make

is successful, then you can proceed to install Postfix (section 6).

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
https://www.postfix.org/.

5 - Porting Postfix to an unsupported system

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.

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.

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.

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.

6 - Installing the software after successful compilation

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.

6.1 - Save existing Sendmail binaries

IMPORTANT: 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.

  * 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.

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

    # 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

6.2 - Create account and groups

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

  * 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:

        /etc/passwd:
            postfix:*:12345:12345:postfix:/no/where:/no/shell

        /etc/group:
            postfix:*:12345:

    Note: there should be no whitespace before "postfix:".

  * 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:

        /etc/group:
            postdrop:*:54321:

    Note: there should be no whitespace before "postdrop:".

6.3 - Install Postfix

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

    # make install       (interactive version, first time install)

    # make upgrade       (non-interactive version, for upgrades)

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

  * 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.

  * If you specify name=value arguments on the "make install" or "make upgrade"
    command line, then these will take precedence over compiled-in default
    settings or main.cf settings.

    The command "make install/upgrade name=value ..." will replace the string
    MAIL_VERSION at the end of a configuration parameter value with the Postfix
    release version. Do not try to specify something like $mail_version on this
    command line. This produces inconsistent results with different versions of
    the make(1) command.

6.4 - Configure Postfix

Proceed to the section on how you wish to run Postfix on your particular
machine:

  * Send mail only, without changing an existing Sendmail installation (section
    7).

  * Send and receive mail via a virtual host interface, still without any
    change to an existing Sendmail installation (section 8).

  * Run Postfix instead of Sendmail (section 9).

7 - Configuring Postfix to send mail only

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.

Follow the instructions in the "Mandatory configuration file edits" in section
10, and review the "To chroot or not to chroot" text in section 11.

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:

    /etc/postfix/master.cf:
        #smtp      inet  n       -       n       -       -       smtpd

Start the Postfix system:

    # postfix start

or, if you feel nostalgic, use the Postfix sendmail command:

    # sendmail -bd -qwhatever

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.

    $ grep -E '(reject|warning|error|fatal|panic):' /some/log/file

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

In order to inspect the mail queue, use one of the following commands:

    $ mailq

    $ sendmail -bp

    $ postqueue -p

See also the "Care and feeding" section 12 below.

8 - Configuring Postfix to send and receive mail via virtual interface

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.

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

    # ifconfig le0:1 <address> netmask <mask> up
    # ifconfig en0 alias <address> netmask 255.255.255.255

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

    /etc/postfix/main.cf:
        myhostname = virtual.host.tld
        inet_interfaces = $myhostname
        mydestination = $myhostname

Follow the instructions in the "Mandatory configuration file edits" in section
10, and review the "To chroot or not to chroot" text in section 11.

Start the Postfix system:

    # postfix start

or, if you feel nostalgic, use the Postfix sendmail command:

    # sendmail -bd -qwhatever

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.

    $ grep -E '(reject|warning|error|fatal|panic):' /some/log/file

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

In order to inspect the mail queue, use one of the following commands:

    $ mailq

    $ sendmail -bp

    $ postqueue -p

See also the "Care and feeding" section 12 below.

9 - Running Postfix instead of Sendmail

Prior to installing Postfix you should save 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:

    # /usr/sbin/sendmail.OFF -q

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

After you have visited the "Mandatory configuration file edits" section below,
you can start the Postfix system with:

    # postfix start

or, if you feel nostalgic, use the Postfix sendmail command:

    # sendmail -bd -qwhatever

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.

    $ grep -E '(reject|warning|error|fatal|panic):' /some/log/file

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

In order to inspect the mail queue, use one of the following commands:

    $ mailq

    $ sendmail -bp

    $ postqueue -p

See also the "Care and feeding" section 12 below.

10 - Mandatory configuration file edits

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.

10.1 - Postfix configuration files

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.

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.

You specify a configuration parameter as:

    /etc/postfix/main.cf:
        parameter = value

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

    /etc/postfix/main.cf:
        other_parameter = $parameter

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.

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:

    # postfix reload

10.2 - Default domain for unqualified addresses

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.

Some examples (use only one):

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

10.3 - What domains to receive locally

Next you need to specify what mail addresses Postfix should deliver locally.

Some examples (use only one):

    /etc/postfix/main.cf:
        mydestination = $myhostname, localhost.$mydomain, localhost
        mydestination = $myhostname, localhost.$mydomain, localhost, $mydomain
        mydestination = $myhostname

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.

10.4 - Proxy/NAT interface addresses

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.

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.

Example: host behind NAT box running a backup MX host.

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

10.5 - What local clients to relay mail from

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:

    /etc/postfix/main.cf:
        mynetworks = 168.100.189.0/28, 127.0.0.0/8

10.6 - What relay destinations to accept from strangers

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):

    /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, ...

10.7 - Optional: configure a smart host for remote delivery

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.

Some examples (use only one):

    /etc/postfix/main.cf:
        relayhost = $mydomain
        relayhost = [mail.$mydomain]

The form enclosed with [] eliminates DNS MX lookups.

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:

    /etc/postfix/main.cf:
        disable_dns_lookups = yes

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

10.8 - Create the aliases database

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.

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.

    /etc/aliases:
        root: you
        postmaster: root
        postfix: root
        bin: root
        etcetera...

Note: there should be no whitespace before the ":".

Finally, build the indexed aliases file with one of the following commands:

    # newaliases
    # sendmail -bi
    # postalias /etc/aliases (pathname is system dependent!)

11 - To chroot or not to chroot

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.

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

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.

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.

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.

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

FreeBSD:

    # mkdir -p /var/spool/postfix/var/run
    # syslogd -l /var/spool/postfix/var/run/log

Linux, OpenBSD:

    # mkdir -p /var/spool/postfix/dev
    # syslogd -a /var/spool/postfix/dev/log

12 - Care and feeding of the Postfix system

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:

    /etc/syslog.conf:
        mail.err                                    /dev/console
        mail.debug                                  /var/log/maillog

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

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.

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

    # postfix check
    # grep -E '(reject|warning|error|fatal|panic):' /some/log/file

  * The first line (postfix check) causes Postfix to report file permission/
    ownership discrepancies.

  * 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.

The DEBUG_README document describes the meaning of the "warning" etc. labels in
Postfix logging.

