This container can be pulled via:
  docker pull registry.opensuse.org/opensuse/factory/totest/containers/opensuse/postfix:3.9
  docker pull registry.opensuse.org/opensuse/factory/totest/containers/opensuse/postfix:3.9-21.42
  docker pull registry.opensuse.org/opensuse/factory/totest/containers/opensuse/postfix:latest

Set DOCKER_CONTENT_TRUST=1 to enable image tag verification.