GitLab CE with Postfix Send Only via Docker

docker-compose.yml

# REF: http://docs.gitlab.com/omnibus/docker/
# REF: https://www.digitalocean.com/community/tutorials/how-to-install-and-configure-postfix-as-a-send-only-smtp-server-on-ubuntu-14-04
# REF: https://github.com/denouche/docker-gitlab/blob/master/Dockerfile
web:
  image: 'myrepo/gitlab-ce-postfix-send-only'
  restart: always
  hostname: 'mysubdomain.mydomain.com'
  environment:
    GITLAB_OMNIBUS_CONFIG: |
      external_url 'http://mysubdomain.mydomain.com'
      # Add any other gitlab.rb configuration here, each on its own line
  ports:
    - '80:80'
    - '443:443'
    - '10022:22'
  volumes:
    - '/srv/gitlab/config:/etc/gitlab'
    - '/srv/gitlab/logs:/var/log/gitlab'
    - '/srv/gitlab/data:/var/opt/gitlab'
    - '/srv/gitlab/postfix/main.cf:/etc/postfix/main.cf'
    - '/srv/gitlab/postfix/aliases:/etc/aliases'

Dockerfile

FROM gitlab/gitlab-ce:latest

RUN echo "postfix postfix/main_mailer_type select Internet Site" | debconf-set-selections \
    && echo "postfix postfix/mailname string mysubdomain.mydomain.com" | debconf-set-selections \
    && apt-get install -y postfix

RUN apt-get install -y \
    mailutils

RUN grep -q postfix-start.sh /assets/wrapper || sed -i \
    '/# Wait for SIGTERM/i # Start postfix service.\nservice postfix start\n' /assets/wrapper

CMD ["/assets/wrapper"]