Outages are inevitable and while the 'cloud' offers many advantages, it is vulnerable to the same issues as on-premises environments.
By the time Microsoft Ignite happens in September 2016, the Outlook app for iOS and Android will have an all-Microsoft infrastructure. The Amazon-based cache is being replaced by a new architecture that is shared by Exchange Online, Exchange on-premises and non-Microsoft email servers like Gmail. It’s a big change and it’s happening now.