Microsoft Exchange Fast Access is a new feature in Microsoft Outlook 2013 that helps improve the email client's startup synchronization time. This improved synchronization time comes is especially helpful for users who have been out of the office for an extended period of time.
With Exchange Fast Access, Outlook 2013 users get the benefit of instant-access that is available through Online Mode, along with the strong synchronization available through Cached Exchange Mode. When Outlook 2013 first boots up, users immediately see their most recent messages and up-to-date calendars, all without affecting the actual user experience.
Administrators can enable/disable the Exchange Fast Access feature through Group Policy objects.