Dockerfile

from ubuntu:12.04
maintainer Vo Minh Thu <noteed@gmail.com>

run apt-get update
run apt-get install -q -y language-pack-en
run update-locale LANG=en_US.UTF-8

run echo mail > /etc/hostname
add etc-hosts.txt /etc/hosts
run chown root:root /etc/hosts

run apt-get install -q -y vim

# Install Postfix.
run echo "postfix postfix/main_mailer_type string Internet site" > preseed.txt
run echo "postfix postfix/mailname string mail.example.com" >> preseed.txt
# Use Mailbox format.
run debconf-set-selections preseed.txt
run DEBIAN_FRONTEND=noninteractive apt-get install -q -y postfix

run postconf -e myhostname=mail.example.com
run postconf -e mydestination="mail.example.com, example.com, localhost.localdomain, localhost"
run postconf -e mail_spool_directory="/var/spool/mail/"
run postconf -e mailbox_command=""

# Add a local user to receive mail at someone@example.com, with a delivery directory
# (for the Mailbox format).
run useradd -s /bin/bash someone
run mkdir /var/spool/mail/someone
run chown someone:mail /var/spool/mail/someone

add etc-aliases.txt /etc/aliases
run chown root:root /etc/aliases
run newaliases

# Use syslog-ng to get Postfix logs (rsyslog uses upstart which does not seem
# to run within Docker).
run apt-get install -q -y syslog-ng

expose 25
cmd ["sh", "-c", "service syslog-ng start ; service postfix start ; tail -F /var/log/mail.log"]