The ability for supplier contacts to acknowledge PO's without a supplier portal account

Summary

PO Acknowledgements for suppliers without Portal access

Content

I have a requirement whereby PO acknowledgements are required from supplier contacts who do not have a supplier portal account. I've checked the documentation and metallink but have not been able to find whether this is possible. 

Scenario: A supplier contact is registered in the system with email address (and assigned to supplier address). PO requiring acknowledgement is created with one of these contacts and communication method set to Email. The notification (which includes PO PDF) will have the option for contact to accept or reject the PO (hyperlinks).

Current fusion solution: we have a customization in place where a custom notification is sent to the contact with a hyperlink to either accept or reject the PO. Crucially supplier contact does not need to enter any credentials - security verification is managed through the notification id.