Switching Notification email to custom domain causes batched notifications for Agents not to be batched anymore

Issue Summary

Having the email notification reduced to batched notifications, makes it easier to know what has changed in one email rather than multiple. However when using custom domain for notifications, the email notification won't be batched anymore

Steps to Reproduce

1. Create a Jira Service Desk Project
2. Claim your domain
3. Configure SPF as mentioned in here to send email on behalf
4. Change the notification scheme email to your custom domain email e.g. support@mydomain.com
5. Have this option select in this Configuration page https://<your-atlassian.net>/secure/admin/SDConfiguration.jspa
   1. No, only send Jira Service Desk notifications to customers (recommended) under Notifications
6. Create a ticket, add yourself as the assignee and another Agent user as watcher and have the ticket assigned to another account that is customer only
7. Make multiple changes on the ticket.

Expected Results

The watcher of the ticket being an Agent should receive batched email notifications

Actual Results

The watcher of the ticket being an Agent, receives multiple notification for each update

Workaround

Currently there is no known workaround for this behavior. A workaround will be added here when available, as the change of email shouldn't affect the behaviour of the notification scheme