There's a new email authentication protocol on the horizon. http://arc-spec.org/ What is ARC? When an email sender or Internet domain owner uses email authentication to make it easier to detect fraudsters sending messages that impersonate their domain, some services like mailing lists or account forwarding may cause legitimate messages to not pass those mechanisms, and then they might not be delivered. These services may be referred to as intermediaries because they receive a message, potentially make some changes to it, and then send it on to one or more other destinations. This kind of email traffic may be referred to as an indirect mailflow. ARC preserves initial email authentication results across subsequent intermediaries (“hops”) that modify the message and thus will cause email authentication to fail to verify when the message reaches its final destination.