UPDATE 4:56 PM

Current Status: Engineers are making progress in reverting the update which is believed to be causing this issue. The update has been reverted in the Latin American region and users hosted from that region should begin to see relief. Reversion of the update in the North American region is underway; as it progresses users there should also experience service restoration.

User Experience: Affected users are unable to send or receive email via the Exchange Online service when using multiple protocols including Outlook, Outlook Web App (OWA), Exchange ActiveSync (EAS), and Exchange Web Services (EWS). Some users may also be unable to access the Exchange Online service.

Customer Impact: A higher than average number of customers are reporting this issue. Analysis indicates that customers will likely have some users experiencing this issue.

Incident Start Time: Wednesday, July 15, 2015, at 9:25 PM UTC

Preliminary Root Cause: Engineers believe that the root cause of this issue is a recent update that is causing higher-than-normal CPU usage on Active Directory infrastructure that handles authentication within and to the service.

Next Update by: Thursday, July 16, 2015, at 12:30 AM UTC

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