Microsoft Office: Jan 24 and Jan 29  

Two outages in the same week wasn't how Microsoft wanted to usher in the new year.

On Jan. 24, the Software-as-a-Service giant reported customers in Europe couldn't access their Office 365 Exchange Online mailboxes that morning.

"We've determined that a subset of Domain Controller infrastructure is unresponsive, resulting in user connection time outs," Microsoft tweeted.

Less than a week later, on January 29, Office 365 struggled with a problem that affected more services and customers across a wider geography.

That outage started somewhat inconspicuously, with Skype for Business dropping calls and reported problems using Microsoft Teams. It then got wider attention as it cascaded to more Office 365, Azure and Dynamics services, with users often unable to log-in to accounts using Azure Active Directory.

Microsoft later blamed an outage at DNS provider CenturyLink, which acknowledged a software defect affecting connectivity to customers' cloud resources.