monitoring prometheus/grafana


I tested on rancher 2 monitoring (prometheus / grafana)
1 / Activation of the monitoring alert-disk-space-rancher2

2 / notification configuration and mail test = Ok
3 / Configuration of alerting = I do not receive the email concerning a warning on the disk space
I have trouble configuring the warning of disk space on the three nodes, could you orient me on the subject?

Best regards