Microsoft has said a “unique” breakdown coupled with a previously unknown flaw in Exchange Online has caused last Tuesday’s extensive outage, PC World has reported. The outages affected Office 365 data centres in North America, said Rajesh Jha, corporate vice president of Office 365 engineering. Without clarifying how many customers were hit. “I want to apologise on behalf of the Office 365 team for the impact and inconvenience this has caused. Email and real-time communications are critical to your business, and my team and I fully recognize our accountability and responsibility as your partner and service provider,” Jha wrote in an incident report posted to the Office 365 support forum.