Current situation:

You can turn batching email notifications on or off. This applies to all projects.

Requested situation:

Being able to turn batching email notifications on or off per project.

The reason is that for Jira Service Desk, it's not always convenient to have batching, since it causes delay in receiving notifications. And since Jira Service Desk is all about Incidents, it causes delay in solving Incidents, which customers don't like.