Yesterday Office 365 and Microsoft Exchange Online went offline and affected businesses that had shifted to the service. Reports of problems accessing email via Exchange Online or Office 365 began appearing around 10 a.m. EST as users signed in and realized that email was not appearing in their in-boxes.
So why did Microsoft Exchange Online and Office 365 go offline?
Microsoft has confirmed the outage and also stated that some clients are experiencing email delays. The outage followed a similar Lync blackout yesterday. Lync is Microsoft’s instant messaging, Internet calling and videoconferencing services to enterprises.
In the future, your can check Office 365 and Microsoft Exchange online service health dashboards for reported issues. http://status.office365.com/