I lead the engineering organization responsible for Office 365. My team builds, operates and supports our Office 365 service, and over the last few days, we have not satisfied our customers' needs. On Thursday, November 8 and today, November 13 we experienced two separate service issues that impacted customers served from our data centers in the Americas. All of these issues have been resolved and the service is now running smoothly. These incidents were unique to the Office 365 Exchange Online mail service, not related to any other Microsoft services.

I'd like to apologize to you, our customers and partners, for the obvious inconveniences these issues caused. We know that email is a critical part of your business communication, and my team and I fully recognize our responsibility as your partner and service provider. We will provide a post mortem, and will also provide additional updates on how our service level agreement (SLA) was impacted. We will be proactively issuing a service credit to our impacted customers.
I also want to provide more detail about the recent issues.

The first event occurred on November 8th from 11:24AM to 7:25PM PST. This service incident resulted in prolonged mail flow delays for many of our customers in North and South America. Office 365 utilizes multiple anti-virus engines to identify and clean virus messages from our customers' inboxes... continued...