A brief outage of Microsoft’s Office 365 service recently caused no major fallout but does point to the inherent vulnerability of cloud service and the importance of a failsafe for enterprise customers.

The service outage, which Microsoft has attributed to a networking interruption at one of its data centers, knocked out its customers’ ability to access the Outlook Web App or send and receive email through Exchange Online on Aug. 17 from approximately 11:30 AM PDT to 2:40 PM PDT. The company said its Service Health Dashboard was updated regularly during the event to notify customers of the problem, though also acknowledge there was a brief period of intermittent access issues to that dashboard.

Microsoft sent a message to its Office 365 users on August 18 in response to the outage. Here is an excerpt:

On August 17, customers served from one of our North America data center lost access to email services included in the Office 365 suite. We apologize for the inconvenience this may have caused you and your employees … Preliminary investigation indicates that a networking interruption in one of our North America data centers caused Office 365 Exchange Online to be inaccessible by some customers … The data center’s networking facilities have been remediated and we are investigating the root cause … We continue to monitor the overall network very closely to maintain high levels of service to customers.

The company also told customers that it would credit affected customers 25 percent of their monthly invoices.