Can we automate the system to send emails when a particular device goes offline?

I would like to receive email for just one or a handful of devices and not all of my devices.

Yes, you can.
You have to turn off notifications in general for all devices by clicking on Settings > Notifications and then Toggling off “Email”. See image below.

Then by clicking on the device you want to receive notices for, and then the device name, then “Configure” in the right pane and toggle Email. See image below.