We are testing Proofpoint, and have a convoluted path where email originates in Orion, is sent to Office 365, sent to PP for evaluation, and then back to Office 365 for delivery to the mailboxes. Unfortunately, the Return-Path header doesn't get set by Office 365 until after the message is returned from PP, so PP thinks the messages violate the bounce management rule of an empty sender. I have found a way in PP to get around this, but if I could fix this at the source in Orion, I would prefer to do that. Does anyone know of a way to set the Return-Path in Orion?