Mail notification for custom attribute
One answer
If you expect it to send mails to the user selected in the "Assign", then the answer is no.
There is no simple mechanism I would be aware of. Maybe you can manage to subscribe the person using JavaScript. I don't know.
You could create Java based server extensions to do the notification. Work Item save follow up actions or asynchronous tasks might be possible.
Also note that A user can basically switch off mail notification. As far as I know it is their privilege to do so.