This container is useful for testing OpenUnison without an email server available for notifications.

Assuming Kubernetes with the namespace blackhole:

$ kubectl create deployment blackhole --image=tremolosecurity/smtp-blackhole -n blackhole
$ kubectl expose deployment/blackhole --type=ClusterIP --port 1025 --target-port=1025 -n blackhole

In the OpenUnison configuration, use the host blackhole.blackhole.svc.cluster.local and the port 1025 with TLS disabled.