Dockerfile

FROM debian:bullseye-slim

EXPOSE 25

ENV POSTFIX_DOMAIN=yourdomain.tld
ENV POSTFIX_MAILNAME=yourreversednsmailhost
ENV POSTFIX_APPEND_VIRTUAL_ALIAS_CF=yes
ENV POSTFIX_APPEND_MYDESTINATION_CF=yes
ENV POSTFIX_TLS_CERT_PATH=smtpd_tls_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem
ENV POSTFIX_TLS_KEY_PATH=smtpd_tls_key_file=/etc/ssl/private/ssl-cert-snakeoil.key

ENV DEBIAN_FRONTEND=noninteractive

RUN apt-get update &&\
    apt-get install -q -y apt-utils
RUN apt-get update &&\
    /bin/bash -c 'debconf-set-selections <<< "postfix postfix/mailname string ${POSTFIX_MAILNAME}"' &&\
    /bin/bash -c 'debconf-set-selections <<< "postfix postfix/main_mailer_type string Internet Site"' &&\
    /bin/bash -c 'debconf-set-selections <<< "opendmarc opendmarc/dbconfig-install boolean false"' &&\
    apt-get install -q -y rsyslog postfix postfix-policyd-spf-python opendkim opendkim-tools opendmarc

ADD opendkim.conf /etc/opendkim.conf
ADD opendmarc.conf /etc/opendmarc.conf
ADD opendmarc_ignore.hosts /etc/opendmarc/ignore.hosts
RUN chown opendmarc:opendmarc -R /etc/opendmarc/ignore.hosts
RUN mkdir -p /var/spool/postfix/opendmarc
RUN chown opendmarc:opendmarc /var/spool/postfix/opendmarc -R
RUN adduser postfix opendmarc
RUN /bin/bash -c 'echo "opendmarc: root" >> /etc/aliases'
ADD main.cf /etc/postfix/main.cf
ADD logrotate.conf /etc/logrotate.conf
ADD rsyslog /etc/logrotate.d/rsyslog

ADD start_script.sh /
RUN chmod +x /start_script.sh

CMD ["/start_script.sh"]