How to customizing PO Email Defaulting Rules in Oracle Fusion Procurement

In Oracle Fusion Procurement/Purchasing, when a PO is created, the current default email communication rule sends notifications to the Supplier Contact email first. If no contact email is available, it then falls back to the Supplier Site email.

Purchase order header fields are defaulted: https://docs.oracle.com/en/cloud/saas/procurement/25c/oaprc/Chunk696293618.html

However, due to our client’s business requirements, we need to reverse this rule by first attempt to send to the Supplier Site email first, it only fall back to the Supplier Contact email if the Supplier Site email is unavailable.

Is there a configuration available to modify this email rule in the application, or would this require customization?