Dockerfile

FROM alpine:3.6
MAINTAINER Pierre GINDRAUD <pgindraud@gmail.com>

ENV RELAY_MYDOMAIN=domain.com \
    RELAY_MYNETWORKS=127.0.0.0/8 \
    RELAY_HOST=[127.0.0.1]:25 \
    RELAY_USE_TLS=yes \
    RELAY_TLS_VERIFY=may \
    RELAY_DOMAINS=\$mydomain \
    RELAY_STRICT_SENDER_MYDOMAIN=true \
    RELAY_MODE=STRICT
    #RELAY_MYHOSTNAME=relay.domain.com
    #RELAY_POSTMASTER=postmaster@domain.com
    #RELAY_LOGIN=loginname
    #RELAY_PASSWORD=xxxxxxxx
    #RELAY_TLS_CA=/etc/ssl/ca.crt


# Install dependencies
RUN apk --no-cache add \
      cyrus-sasl \
      cyrus-sasl-digestmd5 \
      cyrus-sasl-crammd5 \
      postfix \
      rsyslog \
      supervisor \

# Configuration of main.cf
    && postconf -e 'notify_classes = bounce, 2bounce, data, delay, policy, protocol, resource, software' \
    && postconf -e 'bounce_notice_recipient = $2bounce_notice_recipient' \
    && postconf -e 'delay_notice_recipient = $2bounce_notice_recipient' \
    && postconf -e 'error_notice_recipient = $2bounce_notice_recipient' \
    && postconf -e 'inet_interfaces = all' \
    && postconf -e 'inet_protocols = all' \
    && postconf -e 'myorigin = $mydomain' \
# SMTPD auth
    && postconf -e 'smtpd_sasl_auth_enable = yes' \
    && postconf -e 'smtpd_sasl_type = cyrus' \
    && postconf -e 'smtpd_sasl_local_domain = $mydomain' \
    && postconf -e 'smtpd_sasl_security_options = noanonymous' \
# Other configurations
    && postconf -e 'smtpd_banner = $myhostname ESMTP $mail_name RELAY' \
    && postconf -e 'smtputf8_enable = no' \

# Configuration of sasl2
    && mkdir -p /etc/sasl2/ \
    && echo 'pwcheck_method: auxprop' > /etc/sasl2/smtpd.conf \
    && echo 'auxprop_plugin: sasldb' >> /etc/sasl2/smtpd.conf \
    && echo 'mech_list: PLAIN LOGIN CRAM-MD5 DIGEST-MD5' >> /etc/sasl2/smtpd.conf

# copy local files
COPY root/ /

RUN  echo '' > /etc/postfix/aliases \
  && echo '' > /etc/postfix/sender_canonical \
  && mkdir -p /data \
  && ln -s /data/sasldb2 /etc/sasldb2 \
  && chmod +x /start.sh /saslpasswd.sh /listpasswd.sh

EXPOSE 25
VOLUME ["/data"]

CMD ["/start.sh"]