This incident was a result of a failure in a caching service that interfaces with devices using Exchange ActiveSync, including most smart phones. The failure caused these devices to receive an error and continuously try to connect to our service. This resulted in a flood of traffic that our services did not handle properly, with the effect that some customers were unable to access their Outlook.com email and unable to share their SkyDrive files via email. In order to stabilize the overall email service, we temporarily blocked access via Exchange ActiveSync. This allowed us to restore access to Outlook.com via the web and restore the sharing features of SkyDrive.