Microsoft suffered an outage of its Office 365 platform yesterday (17th August). The outage affected North America and was offline for a number of hours. The problems at the particular data centre affected some of Microsoft’s other services too such as, CRM Online and SkyDrive. It shortly became aware that the problem was only affecting email services, SharePoint Online and Lync remained operational. Microsoft later said in a statement that it took any service disruption very seriously and that any customers affected would be reimbursed their service charges per the conditions in the service level agreement.
More details on the story can be found here.