Email Notification - Delivery Note Copy to Transporter Email ID


I would like to create a custom email notification - where a delivery note is sent to the transporter primary email id in addition to the customer getting one.

When creating a custom email notification - Under Recipients - if I select by document field contact_email - email copy correctly goes to customer. If I add/select recipient by Role - Supplier - it has no effect and no email is sent out to Supplier (is_transporter).

How do I resolve this issue?