mailman: Enable VERP

Improve bounce detection.

Also reduce the number of recipients per single SMTP delivery.

.gitlab-ci.yml

@@ -10,6 +10,8 @@ variables:
 docker_build_and_release_tests:
   stage: docker_build
   image: quay.io/podman/stable
+  variables:
+    IMAGE_TAG: $CI_REGISTRY_IMAGE:$CI_COMMIT_REF_SLUG
   script:
     - echo -n "$CI_JOB_TOKEN" | podman login -u gitlab-ci-token --password-stdin $CI_REGISTRY
     - cd test && podman build --build-arg ci_token=$CI_JOB_TOKEN --pull -t $IMAGE_TAG .