1 - Purpose of this document ============================ 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. - Replace sendmail altogether. 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 HTML web pages (point your browser to html/index.html) and as UNIX-style man pages (point your MANPATH environment variable to the `man' subdirectory; be sure to use an absolute path). The sample configuration files in the `conf' directory have extensive comments, but they may not describe every nuance of every feature. Many 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 ================================== If your system is supported, it is one of AIX 3.2.5 AIX 4.1.x AIX 4.2.0 AIX 4.3.x AIX 5.2 BSD/OS 2.x BSD/OS 3.x BSD/OS 4.x Darwin 1.x FreeBSD 2.x FreeBSD 3.x FreeBSD 4.x FreeBSD 5.x HP-UX 9.x HP-UX 10.x HP-UX 11.x IRIX 5.x IRIX 6.x Linux Debian 1.3.1 Linux Debian 2.x Linux RedHat 3.x (August 2002) Linux RedHat 4.x Linux RedHat 5.x Linux RedHat 6.x Linux RedHat 7.x Linux Slackware 3.x (long ago) Linux Slackware 4.x Linux Slackware 7.x Linux SuSE 5.x Linux SuSE 6.x Linux SuSE 7.x Mac OS X NEXTSTEP 3.x (long ago) NetBSD 1.x OPENSTEP 4.x OSF1.V3 (Digital UNIX) OSF1.V4 aka Digital UNIX V4 OSF1.V5 aka Digital UNIX V5 OpenBSD 2.x OpenBSD 3.x Reliant UNIX 5.x Rhapsody 5.x SunOS 4.1.x (December 2002) SunOS 5.4..5.8 (Solaris 2.4..8) Ultrix 4.x (well, that was long ago) or something closely resemblant. 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 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. 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 % make tidy first. This will get rid of any system dependencies left over from compiling the software elsewhere. 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: % 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 is turned off automatically. In order to build with non-default settings, for example, with a configuration directory other than /etc/postfix, use: % make makefiles CCARGS='-DDEF_CONFIG_DIR=\"/some/where\"' % make Be sure to get the quotes right. These details matter a lot. Parameters whose defaults can be specified in this way are: Macro name default value for typical default ----------------------------------------------------------- DEF_COMMAND_DIR command_directory /usr/sbin DEF_CONFIG_DIR config_directory /etc/postfix DEF_DAEMON_DIR daemon_directory /usr/libexec/postfix DEF_MAILQ_PATH mailq_path /usr/bin/mailq DEF_MANPAGE_DIR manpage_directory /usr/local/man DEF_NEWALIAS_PATH newaliases_path /usr/bin/newaliases DEF_README_DIR readme_directory no (do not install) DEF_SAMPLE_DIR sample_directory /etc/postfix DEF_SENDMAIL_PATH sendmail_path /usr/sbin/sendmail In order to build Postfix for very large applications, where you expect to run more than 1000 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 In any case, if the command % make produces compiler error messages, it may be time to examine the FAQ document (see html/faq.html). 5 - Porting to on an unsupported system ======================================= - Each system type is identified by a unique name. Examples: SUNOS5, FREEBSD4, and so on. 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 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, not the emulated one. - Add an #ifdef SYSTEMTYPE section to the central util/sys_defs.h include file. You may have to invent new feature macros. Please choose sensible feature macro names such as HAS_DBM or FIONREAD_IN_SYS_FILIO_H. I strongly recommend against #ifdef SYSTEMTYPE dependencies in individual source files. This may seem to be the quickest solution, but it will create a mess that becomes increasingly difficult to maintain over time. Moreover, with the next port you'd have to place #ifdefs 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. 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. As superuser, 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 In order to install or upgrade Postfix: - 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 file entry looks like this: postfix:*:12345:12345:postfix:/no/where:/no/shell Note: there should be no whitespace before "postfix:". - Make sure there is a corresponding alias in /etc/aliases: postfix: root 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: postdrop:*:54321: Note: there should be no whitespace before "postdrop:". - Optional: If you want to install symbol-stripped (non-debug) versions of the Postfix programs and daemons, do: % strip bin/* libexec/* - 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 non-interactive version needs the /etc/postfix/main.cf file from a previous installation. If the file does not exist, use interactive installation instead. The interactive version offers suggestions for pathnames that you can override interactively, and stores your preferences in /etc/postfix/main.cf for convenient future upgrades. - 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). - Replace sendmail altogether (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. Start the Postfix system: # postfix start or, if you feel nostalgic, use the Postfix sendmail command: # sendmail -bd -qwhatever and watch your syslog file for any error messages. % egrep '(reject|warning|error|fatal|panic):' /some/log/file Typical logfile names are: /var/log/maillog or /var/log/syslog. See /etc/syslog.conf for actual logfile names. In order to inspect the mail queue, use % sendmail -bp See also the "Care and feeding" section 12 below. 8 - Configuring Postfix to send and receive mail (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. The examples/virtual-setup directory gives instructions for setting up virtual interfaces for a variety of UNIX versions. In the /etc/postfix/main.cf file, I would specify 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 mail system: # postfix start or, if you feel nostalgic, use the Postfix sendmail program: # sendmail -bd -qwhatever and watch your syslog file for any error messages. % egrep '(reject|warning|error|fatal|panic):' /some/log/file Typical logfile names are: /var/log/maillog or /var/log/syslog. See /etc/syslog.conf for actual logfile names. In order to inspect the mail queue, use % sendmail -bp See also the "Care and feeding" section 12 below. 9 - Turning off sendmail forever ================================ Prior to installing Postfix you should save the 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 After you have visited the "Mandatory configuration file edits" section below, you can start the Postfix system with # postfix start But the good old sendmail way works just as well: # sendmail -bd -qwhatever and watch the syslog file for any complaints from the mail system. % egrep '(reject|warning|error|fatal|panic):' /some/log/file Typical logfile names are: /var/log/maillog or /var/log/syslog. See /etc/syslog.conf for actual logfile names. See also the "Care and feeding" section 12 below. 10 - Mandatory configuration file edits ======================================= By default, Postfix configuration files are in /etc/postfix, and must be owned by root. Giving someone else write permission to main.cf or master.cf means giving root privileges to that person. Whenever you make a change to a config file, execute the following command in order to refresh a running mail system: # postfix reload In /etc/postfix/main.cf you will have to set up a minimal number of configuration parameters. Postfix configuration parameters resemble shell variables. You specify a variable as parameter = value and you use it by putting a $ in front of its name: other_parameter = $parameter You can use $parameter before it is given a value. The Postfix configuration language uses lazy evaluation, and does not look at a parameter value until it is needed at runtime. 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: myorigin = $myhostname myorigin = $mydomain In the first case, local mail goes out as user@$myhostname, in the second case the sender address is user@$mydomain. Next you need to specify what mail addresses Postfix should deliver locally. Some examples: mydestination = $myhostname, localhost.$mydomain mydestination = $myhostname, localhost.$mydomain, $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. 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. The default setting includes all class A, B or C networks that the machine is attached to. Often, that gives relay permission to too many clients. My own settings are: mynetworks = 184.108.40.206/28, 127.0.0.0/8 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: relayhost = $mydomain relayhost = mail.$mydomain relayhost = [mail.$mydomain] The form enclosed with  eliminates DNS MX lookups. By default, the SMTP client will do DNS lookups for sender and recipient addresses 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: disable_dns_lookups = yes The FAQ (html/faq.html) has more hints and tips for firewalled and/or dial-up networks. Finally, if you haven't used Sendmail prior to using Postfix, you will have to build the alias database (with: sendmail -bi, or: newaliases). Be sure to set up aliases for root and postmaster that forward mail to a real person. Postfix has a sample aliases file conf/aliases that you can adapt to local conditions. 11 - To chroot or not to chroot =============================== Postfix can run most daemon processes in a chroot jail, that is, 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 the Postfix daemons that deliver mail locally, every Postfix daemon can run chrooted. Sites with high security requirements should consider to chroot all daemons that talk to the network: the smtp and smtpd processes, and perhaps also the lmtp client. 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 has a collection of scripts that help you set up chroot environments for Postfix systems. IMPORTANT: if you enable chrooted operation of the SMTP server you must copy the passwd file into the chroot jail, otherwise the SMTP server will reject mail for local addresses. 44BSD systems: # mkdir /var/spool/postfix/etc # cp /etc/pwd.db /var/spool/postfix/etc Other systems: # mkdir /var/spool/postfix/etc # cp /etc/passwd /var/spool/postfix/etc You may also have to copy /etc/nsswitch.conf and the files referenced by /etc/nsswitch.conf. See the system dependent scripts in examples/chroot-setup for suggestions. 12 - Care and feeding of the Postfix system =========================================== The Postfix programs log all problems to the syslog daemon. The names of logfiles are specified in /etc/syslog.conf. Note: the syslogd will not create files. You must create them ahead of time before (re)starting syslogd. At the very least you need something like: mail.err /dev/console mail.debug /var/log/maillog 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 # egrep '(reject|warning|error|fatal|panic):' /some/log/file Typical logfile names are: /var/log/maillog or /var/log/syslog. See /etc/syslog.conf for actual logfile names. 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 anti-relay and anti-UCE blocks are.