groups:
  - name: mail
    rules:
    # Alert for any instance that is unreachable for >1 minutes.
    - alert: InstanceDown
      expr: up == 0
      for: 1m
      labels:
           severity: page
      annotations:
           summary: "Instance {{ $labels.instance }} down"
           description: "{{ $labels.instance }} of job {{ $labels.job }} has been down for more than 5 minutes."