Outlook.com REST API - Backwards compatability with LiveID Live SDK

Question

I'm using the new unified Outlook Rest API and it works great for Office 365 accounts but Outlook.com accounts often throw MailboxNotEnabledForRESTAPI exception. I understand there is transition going on now that will move all existing accounts to the new API. Is there an example on how to implement a backwards compatible call to the older LiveId/Windows Live SDK? The application registration portal has a check box under advanced called "Live SDK Support". What does this mean and how do I write fall back logic when a user uses my service and they have not been transitioned? Any help would be appreciated as we are trying to ship this service in the next day or so.