Dockerfile

FROM debian:10-slim as builder
ARG version=3.6.0
ARG INSTALL_ROOT=/postfix
ARG POSTFIX_PACKAGE_DIR=/postfix-package

RUN apt update && \
    apt install -y make gcc postgresql-server-dev-all wget libdb-dev m4 && \
    rm -f /var/cache/apt/archives/*.deb
RUN wget http://cdn.postfix.johnriley.me/mirrors/postfix-release/official/postfix-${version}.tar.gz
RUN tar xvf postfix-${version}.tar.gz

WORKDIR /postfix-${version}
RUN make tidy
RUN make -f Makefile.init makefiles shared=yes dynamicmaps=yes \
        'CCARGS=-DHAS_PGSQL -I/usr/include/postgresql' \
        'AUXLIBS_PGSQL=-L/usr/lib -lpq'
RUN make non-interactive-package install_root=${INSTALL_ROOT}

RUN mkdir ${POSTFIX_PACKAGE_DIR} && \
    cd ${INSTALL_ROOT} && \
    find . \! -type d -print | xargs tar rf ${POSTFIX_PACKAGE_DIR}/outputfile && \
    gzip ${POSTFIX_PACKAGE_DIR}/outputfile

FROM debian:10-slim
ARG POSTFIX_PACKAGE_DIR=/postfix-package

COPY --from=builder /${POSTFIX_PACKAGE_DIR}/outputfile.gz /
RUN umask 022 && \
    gzip -d < outputfile.gz | (cd / ; tar xvpf -) && \
    apt update && apt install -y inetutils-syslogd && \
    rm -rf /var/cache/apt/archives

RUN useradd postfix && groupadd postdrop
RUN chown :postdrop /usr/sbin/postqueue /usr/sbin/postdrop && \
    chmod g+s /usr/sbin/postqueue /usr/sbin/postdrop
RUN mkdir /var/spool/postfix

EXPOSE 25
COPY docker-entrypoint.sh /
ENTRYPOINT [ "/bin/bash", "docker-entrypoint.sh" ]