4. Microsoft Office 365
Microsoft Office 365 customers were hit twice in November by outages that knocked out their email service.
"All of us in the Office 365 team and at Microsoft appreciate the serious responsibility we have as a service provider to you, and we know that any issue with the service is a disruption to your business -- that's not acceptable," wrote Rajesh Jha, corporate vice president of the Microsoft Office Division, in a blog post about the outages.
Customers in North and South America suffered an eight-hour outage of their Office 365 Exchange Online service on Nov. 8, resulting in "prolonged mail flow delays" for customers, Jha said. The second email service outage, on Nov. 15, lasted for more than five hours.