How to get email alerts notification on when any of Windows Server machines get DOWN with SCOM 2012 R2

Hello Expert,

I have created a group which contains Windows Servers and SCOM able to generate heartbeats alerts when these servers get down and email alerts are configured and working properly when any alerts get on SCOM,it will able to send email alerts notification.
But I need only to get email notification when Servers get down then what are the Subscription criteria used for getting email notification alerts when servers of a particular group is down.

Please assist me to finding the solution for this.

Thanks
Richa KM