This is useful mostly for playbooks that run unattended and for a limited set of systems. In case of provisioninging this plugin (together with a final mail action) helps to get notified when something went wrong, or when the installation finished successfully.

Unfortunately, there is no way to enable/disable a plugin from a playbook. So installing the plugin means all other use-cases (provisioning, troubleshooting, reporting or management) all send mails on failure. Something we may want to fix in the future...