Microsoft Teams today went down due to an expired SSL certificate! This is another example of a fundamental component of the web infrastructure of a major company not being adequetely monitored.
We’ve determined that an authentication certificate has expired causing, users to have issues using the service. We’re developing a fix to apply a new certificate to the service which will remediate impact. Further updates can be found under TM202916 in the admin center. - @MSFT365Status
TrackSSL is a simple service that does one job well - it monitors your SSL certificates and send you notifications before your certificates expire.
Posted 3rd February 2020