made postfix Alpine based

postfix/Dockerfile

@@ -1,15 +1,21 @@
 # syntax=docker/dockerfile:1.3-labs
-FROM ubuntu:20.04
+FROM alpine:latest
 # install apt packages
+ENV TZ Europe/Berlin 
+RUN apk add --no-cache postfix spamassassin rsyslog logrotate xz
+# install s6 process manager
+ADD https://github.com/just-containers/s6-overlay/releases/download/v3.1.1.2/s6-overlay-noarch.tar.xz /tmp
+ADD https://github.com/just-containers/s6-overlay/releases/download/v3.1.1.2/s6-overlay-x86_64.tar.xz /tmp
 RUN <<EOF 
-apt-get update -y
-export DEBIAN_FRONTEND=noninteractive 
-export TZ=Europe/Berlin 
-apt-get install -y tzdata postfix spampd wget xz-utils
-apt-get autoclean
-rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/* ~/.cache ~/.npm
+tar -C / -Jxpf /tmp/s6-overlay-noarch.tar.xz
+tar -C / -Jxpf /tmp/s6-overlay-x86_64.tar.xz
+rm /tmp/s6-overlay*.tar.xz
 EOF
+COPY ./etc/s6-overlay /etc/s6-overlay
+COPY ./etc/postfix /etc/postfix
+# install kopano core
 WORKDIR /root
 EXPOSE 25
 VOLUME /var/spool/postfix
-ENTRYPOINT ["/usr/sbin/postmulti -i %i -p start"]
+# HEALTHCHECK --start-period=350s CMD echo QUIT|nc localhost 25|grep "220 .* ESMTP Postfix"
+ENTRYPOINT ["/init"]