Outlook.com had a 2 + day outage which has resulted in some users not being able to get access their e - mail for the better part of this past week . 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 . These parts of the service were fully stabilized within a few hours of the initial incident . A significant backlog of Exchange ActiveSync requests accumulated as we worked to stabilize access . To avoid another flood of traffic , we needed to restore access to Exchange ActiveSync slowly , which meant that some customers remained impacted for a longer period of time . ;