We need a alert mail when there are no datapoints

I need to create an alert mail if there are no data points. We have the bunch of servers(250). We build grafana dashboard for these servers to check server health. In that for each server, we read CPU, RAM, and DISK space from each server. I need grafana alerts to trigger when there is no data streaming in any of the servers so that I can infer that the container is down. Currently, the graph just stops plotting and no alerts are triggered.
If the condition has “HAS NO VALUE” and there are no datapoint by any one of the servers. I need an alert mail, from that server we don’t get any data point.
Please help this. Thanks in advance.
This is my query:

This is my alert rule:

Here I stop server stats in one of my servers. Saw if the mail has come or not?
but I didn’t get any mail. How can get mail alert if any one of the servers went down and something is wrong with that server?

What does the test rule return?

You can see the Test rule return value above query in following screen shot. Thanks!