Microsoft Teams outage blamed on expired SSL certificate

Microsoft Teams downed for three hours due to simple error

The three-hour outage affecting Microsoft Teams yesterday was due to an expired SSL certificate that had not been renewed.

Users attempting to sign-in early yesterday afternoon were greeted with an error message, indicating that HTTPS connections to Microsoft's servers had failed.

"We've determined that an authentication certificate has expired causing users to have issues using the service," Microsoft admitted in its outage notification. "We're developing a fix to apply a new certificate to the service which will remediate impact."

The issue took around three hours to fix for most users, although it took the company several more hours until it could announce that it had been fully resolved.

The outage will be particularly embarrassing for Microsoft, with Teams competing against the vastly more popular Slack collaboration tool. While Microsoft has sought to push Teams as an integral part of Office 365, subscribers complain that it is clunky compared to Slack for all but the most simplistic of uses.

Nevertheless, Microsoft claims around 20 million users worldwide for Teams.

Microsoft reportedly considered tabling an $8 billion bid to acquire Slack in 2016, but co-founder and board member Bill Gates pushed, instead, for the company to improve the unloved Skype for Business too. Microsoft Teams was unveiled as a direct competitor to Slack in November 2016.

In July last year, Microsoft introduced a free version of Teams to compete with Slack, which enables its collaboration tool to be used for free, albeit limiting the number of posted messages to 10,000.

Nevertheless, Microsoft has struggled to persuade organisations that Teams is a better product than Slack with, for example, former Blenheim Chalcot CIO Mark Ridley describing it as a "confusing set of tools".