Beyond Linux From Scratch - Version 5.1

Part VI. Server Networking

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Mail Server Software

MTAs are the programs which transport mail from one machine to the other. The traditional MTA is Sendmail, however there are several other choices.

As well as SMTP servers there is a POP server (qpopper) and an IMAP server (Courier-IMAP).

Postfix-2.1.1

Introduction to Postfix

The Postfix package contains a Mail Transport Agent (MTA). This is useful for sending email to other users of your host machine. It can also be configured to be a central mail server for your domain, a mail relay agent or simply a mail delivery agent to your local Internet Service Provider (ISP).

Package information

Postfix dependencies

Required

Berkeley DB-4.2.52.2

Optional

Cyrus SASL

Installation of Postfix

Before you compile the program, you need to create users and groups that will be expected to be in place when the install script executes. Add the users and groups with the following commands: 

groupadd postfix &&
groupadd postdrop &&
groupadd -g 65534 nogroup &&
useradd -c postfix -d /dev/null -g postfix -s /bin/false postfix &&
useradd -c nobody -d /home -g nogroup -s /bin/bash -u 65534 nobody &&
chown postfix:postfix /var/mail

Install postfix by running the following commands: 

make &&
sh postfix-install daemon_directory=/usr/sbin \
                   manpage_directory=/usr/share/man \
                   sample_directory=/usr/share/doc/postfix \
                   -non-interactive

The final installation step is to install the program's documentation with this command: 

install -d /usr/share/doc/postfix &&
cp -rf html/* /usr/share/doc/postfix

Command explanations

sh postfix-install ... -non-interactive : We don't want the install script to ask any questions so we call it with a non-interactive switch and accept default destination directories in all but three cases.

Configuring Postfix

Config files

/etc/aliases, /etc/postfix/main.cf and /etc/postfix/master.cf

Configuration Information 

cat >> /etc/aliases << "EOF"
# Begin /etc/aliases

MAILER-DAEMON:    postmaster
postmaster:       root

root:             LOGIN
# End /etc/aliases
EOF
[Note]

Note

To protect an existing /etc/aliases file, we will append these aliases to it if it exists. This file should be checked and duplicate aliases removed, if present.

The /etc/aliases file that was just created or appended, the main.cf and the master.cf must be personalized for your system. The aliases file needs your non-root login identity so mail addressed to root can be forwarded to you at the user level. The main.cf file needs your fully qualified hostname. All of these edits can be done with sed commands entered into the console with appropriate substitutions of your non-root login name for [user] and your fully qualified hostname for [localhost.localdomain]. You will find the main.cf file is self documenting, so load it into your editor to make the changes you need for your situation. 

cp /etc/aliases /etc/aliases.bak &&
cp /etc/postfix/main.cf /etc/postfix/main.cf.bak &&
sed "s/LOGIN/[user]/" /etc/aliases.bak > /etc/aliases &&
sed "s/#myhostname = host.domain.tld/myhostname = \ 
        [localhost.localdomain]/" \
        /etc/postfix/main.cf.bak > /etc/postfix/main.cf &&
/usr/bin/newaliases &&
/usr/sbin/postfix start

Postfix init.d script

To automate the running of Postfix at startup, install the /etc/rc.d/init.d/postfix init script included in the blfs-bootscripts-5.1 package. 

make install-postfix

Contents

The Postfix package contains bounce , cleanup, error, flush, lmtp, local, mailq, master, newaliases, nqmgr, pickup, pipe, postalias, postcat, postconf, postdrop, postfix, postkick, postlock, postlog, postmap, postqueue, postsuper, qmgr, qmqpd, sendmail, showq, smtp, smtpd, spawn, trivial-rewrite, and virtual.

Description

postfix

postfix is the program that starts and stops the mail delivery system.

master

master is the resident process that runs bounce, cleanup, error, flush, lmtp, local, nqmgr, pickup, pipe, qmgr, qmqpd, showq, smtp, smtpd, spawn, trivial-rewrite and virtual on demand. These programs are not designed to work as user commands.

postqueue

postqueue implements the Postfix user interface for queue management. It implements all the operations that are traditionally available via the sendmail command.

sendmail

sendmail implements the Postfix to Sendmail compatibility interface. mailq and newaliases are symlinks to sendmail.

showq

showq will emulate the mailq command when the Postfix mail system is not running.

postsuper

postsuper does maintenance jobs on the Postfix queue.

postalias

postalias creates, queries or updates Postfix alias databases.

postcat

postcat prints the contents of a Postfix queue file in human-readable form.

postconf

postconf prints or changes the value of configuration parameters.

postdrop

postdrop creates a file in the maildrop directory and copies its standard input to the file.

postkick

postkick makes the mail system private IPC accessible for use in shell scripts.

postlock

postlock locks a file for exclusive access and executes a command on that file.

postlog

postlog implements a logging interface for use in shell scripts.

postmap

postmap creates, queries or updates Postfix lookup tables.

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