Implement docker-compose setup for CAcert software

smtp.Dockerfile

@@ -0,0 +1,29 @@
+FROM debian:buster
+
+RUN apt-get update \
+    && DEBIAN_FRONTEND=noninteractive \
+    apt-get install -y --no-install-recommends \
+    ca-certificates \
+    curl \
+    dumb-init \
+    mutt \
+    postfix \
+    postfix-pcre \
+    psmisc \
+    && apt-get clean \
+    && rm -rf /var/lib/apt/lists/*
+
+EXPOSE 25
+
+RUN adduser --uid 1000 --gecos "catchall mailbox" --disabled-password catchall ; \
+    postconf home_mailbox=Maildir/ ; \
+    postconf maillog_file=/dev/stdout ; \
+    postconf mailbox_command= ; \
+    postconf virtual_alias_maps=pcre:/etc/postfix/virtual ; \
+    echo '/.*/ catchall' > /etc/postfix/virtual
+
+VOLUME /home/catchall/Maildir
+
+COPY docker/run-postfix /usr/local/bin/run-postfix
+
+CMD ["dumb-init", "/usr/local/bin/run-postfix"]