Problem

'Send mail for this update' checkbox in the bulk change process currently defaults to ticked/true. Bulk change users often overlook this checkbox and inadvertently trigger multiple notifications, spamming users associated with issues in context. Statistically most users would opt to NOT 'Send mail for this update' and it therefore it makes sense from this checkbox to default to UNTICKED. Furthermore Jira Cloud already defaults to UNTICKED and it makes sense for Jira DC to align to this.

Suggested Solution

Suggesting that make 'Send mail for this update' checkbox be unticked for users to prevent unnecessary notifications for each Bulk operations

Workaround 1

With the script below, non-admin users will have the Send mail for this update unchecked as default. Jira Administrators will still have the option to turn it on.

This can be achieved by pasting the code below in your Annoucement field, within the Annoucement Banner settings.

For reference: Configuring an announcement banner

<script>
document.addEventListener('DOMContentLoaded', function() {
if (window.location.pathname.includes('/bulkedit/') && document.getElementById('sendBulkNotification')) {
    document.getElementById('sendBulkNotification').value = false;
}
});
</script>

Workaround 2

We can disable mail notifications for a particular bulk operation by deselecting the Send Notification checkbox in the bulk operation wizard. For this option to be available, we must be an administrator or project administrator of all the projects associated with selected issues. 

Disable customer notifications - Some bulk operations, such as Change comment, might trigger email notifications to your customers. To prevent a flurry of emails, a Jira admin can temporarily disable outgoing mail in   > System > Mail > Outgoing mail. This setting controls both Jira and customer notifications, so remember to turn it back on when you're done with your bulk edit.