Revised package installation and cleanup process

Package installation is now run in one command.
Cleanup process is now done at end of script.

Dockerfile

@@ -1,14 +1,18 @@
 FROM ubuntu:14.04
 MAINTAINER Thomas VIAL
 
+
+ENV DEBIAN_FRONTEND noninteractive
+
 # Packages
-RUN apt-get update -q --fix-missing
-RUN apt-get -y upgrade
-RUN DEBIAN_FRONTEND=noninteractive apt-get -y install vim postfix sasl2-bin courier-imap courier-imap-ssl \
+RUN apt-get update && \
+  apt-get upgrade -y --no-install-recommends && \
+  apt-get install -y --no-install-recommends vim postfix sasl2-bin courier-imap courier-imap-ssl \
     courier-pop courier-pop-ssl courier-authdaemon supervisor gamin amavisd-new spamassassin clamav clamav-daemon libnet-dns-perl libmail-spf-perl \
     pyzor razor arj bzip2 cabextract cpio file gzip nomarch p7zip pax unzip zip zoo rsyslog mailutils netcat \
     opendkim opendkim-tools opendmarc curl fail2ban
-RUN apt-get autoclean && rm -rf /var/lib/apt/lists/*
+
+
 
 # Configures Saslauthd
 RUN rm -rf /var/run/saslauthd && ln -s /var/spool/postfix/var/run/saslauthd /var/run/saslauthd
@@ -59,6 +63,12 @@ RUN curl https://letsencrypt.org/certs/lets-encrypt-x2-cross-signed.pem > /etc/s
 ADD start-mailserver.sh /usr/local/bin/start-mailserver.sh
 RUN chmod +x /usr/local/bin/start-mailserver.sh
 
+
+RUN apt-get clean && \
+  rm -rf /tmp/* /var/tmp/* && \
+  rm -rf /var/lib/apt/lists/*
+
+
 # SMTP ports
 EXPOSE  25
 EXPOSE  587