From ubuntu:xenial MAINTAINER Andre Peters ENV DEBIAN_FRONTEND noninteractive RUN apt-get update RUN apt-get -y install supervisor \ postfix \ sasl2-bin \ postfix \ postfix-mysql \ postfix-pcre \ rsyslog \ ca-certificates COPY supervisord.conf /etc/supervisor/supervisord.conf COPY postfix.sh /opt/postfix.sh RUN groupadd -g 5000 vmail RUN useradd -g vmail -u 5000 vmail -d /var/vmail EXPOSE 588 CMD exec /usr/bin/supervisord -c /etc/supervisor/supervisord.conf