Hey there, @gLocal916.
Welcome to the Community!
The best way to make the Proofpoint error go away when trying to pay an invoice online would be to get in touch with them. Proofpoint helps protect people, data and brands against cyber attacks. Offering compliance and cybersecurity solutions for email, web, cloud, and more.
The error they are receiving isn't associated with any of the QuickBooks products and is happening outside of the QuickBooks product.
Feel free to come back and let us know how it goes. Have a wonderful day!
