After creating an upstream payment application that bills against a client contract, funding or main contract, you can send a copy of the payment application's 'Detail' tab to your upstream collaborator to review. Once reviewed, your collaborator can then reply directly to that message to indicate that they have approved your payment application for payment (or to supply you with a reason for rejecting your payment application). To ensure that your collaborator's response is captured in writing, Procore saves all replies to your outgoing message's 'From' address in the Emails tab on the payment application.