This container can be pulled via:
  docker pull registry.opensuse.org/home/kukuk/container/opensuse/postfix:3.10.4
  docker pull registry.opensuse.org/home/kukuk/container/opensuse/postfix:3.10.4-5.341
  docker pull registry.opensuse.org/home/kukuk/container/opensuse/postfix:latest

Set DOCKER_CONTENT_TRUST=1 to enable image tag verification.