“Dual Delivery” is a new feature for Google Message Security that “enables incoming email messages to be copied and sent to two different mailhosts, Dual Delivery gives users a chance to familiarize with new email platform without disrupting existing system. It also gives IT a chance to learn from user behavior and understand technical implications of migration before a full rollout. DD also makes it easier to pilot and migrate to Google Apps. By enabling "Send a copy to Google Apps Gmail" feature of DD, you can test Gmail without interrupting current practice. If you choose to switch over to GA, you can enable "Use Google Apps Gmail" feature in Administration Console to directly route all mail to Gmail without having to manually reroute your MX records. DD can also be used as a secondary email access point. If users’re unable to access primary mailbox, or if admins want to give users cloud-based remote or mobile email access, DD can provide read/write email access through secondary inbox. Dual Delivery is now available to Postini through Delivery Manager settings in Postini Administration Console,” explain Google.