It’s odd that Microsoft would forget to renew a critical authentication certificate, and it was rude timing, as so many were attempting to log in and start their week.

Almost three years old, Microsoft Teams is the company’s Slack competitor. Last year, it added new features like private channels and custom video chat backgrounds, and it recently launched its first TV ad campaign. Needless to say, today’s outage probably doesn’t help in Microsoft’s efforts to take on Slack.