Also read on that page:
IMPORTANT: Sometime in second quarter of 2022 we will selectively pick tenants and disable Basic Auth for all affected protocols except SMTP AUTH for a period of 12-48 hours. After this time, Basic Auth for these protocols will be re-enabled, if the tenant admin has not already re-enabled them using our self-service tools.
So it could be that you are one of the chosen ones if it works later again. Can you still send mails?