Postfix mail transfer agent

Postfix version

Tested with Postfix 1.1.11.

Introduction

Postfix is a mail transfer agent that has a good reputation for being fast and secure.

Debian installs Exim by default, but we've switched to Postfix because it works quite well with Sympa virtual hosts.

Installation

Make sure that /etc/hosts and /etc/resolv.conf are set up correctly, as described in StandardConfigFiles. (If you change these later, you'll need to restart Postfix using /etc/init.d/postfix restart.)

sudo apt-get install postfix

Then install /etc/postfix/main.cf, changing myserver and myserver.example.org for your server's hostname and domain, and changing 10.0.0.240/29 to your network address. If your server isn't meant to handle mail for the example.org domain (e.g. to someone@example.org), remove $mydomain from the mydestination line.

Make sure Postfix has an alias database:

sudo newaliases

Tell Postfix to reload its configuration:

sudo postfix reload

Maildir mailboxes

We're going to use maildir format for mailboxes, because it's more reliable than the standard mbox format.

Create a file /etc/procmailrc containing:

DEFAULT=$HOME/Maildir/

Change /etc/login.defs so it contains:

QMAIL_DIR      Maildir/
#MAIL_DIR      /var/mail
MAIL_FILE      Maildir/

In /etc/pam.d/login, change the line about pam_mail.so so it reads:

session optional pam_mail.so standard dir = ~/Maildir/

Make sure the MAIL environment variable is set in /etc/profile as described in StandardConfigFiles.

Tell Postfix to reload its configuration:

sudo postfix reload

Procmail will create each user's ~/Maildir when delivering the first message.

Next, see StandardSpamassassin for instructions on installing a spam filter.

Testing

Send an email to your normal user account on your server, and see if it arrives. You can check your mail on the server using mutt.

Make sure your server isn't an open mail relay; test it using the Network Abuse Clearinghouse's mail relay testing service.

Virtual hosts

In /etc/postfix/main.cf, this line tells tells Postfix to read a regular expression table containing aliases for addresses in virtual domains:

virtual_maps = regexp:/etc/postfix/virtual

To add a virtual host, add entries to the file /etc/postfix/virtual. At minimum, you'll need one line to declare the virtual host, as well as lines for postmaster, mailer-daemon and abuse, like this:

# Virtual alias table for example.info
/^example\.info$/                        DOMAIN
/^postmaster@example\.info$/             postmaster
/^mailer-daemon@example\.info$/          mailer-daemon
/^abuse@example\.info$/                  abuse

The DOMAIN value in the right column is a dummy entry, but it must be there. The other values in the right column refer to aliases in /etc/aliases.

After changing this file, run:

sudo postmap /etc/postfix/virtual

If you change /etc/aliases, run:

sudo newaliases

If you change /etc/postfix/main.cf, run:

sudo postfix reload

Upgrading

It appears that the variable virtual_maps has been renamed virtual_alias_maps in newer versions of Postfix. Keep this in mind when upgrading.
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