Back in 2019 Microsoft announced they were turning off Basic Authentication for all Exchange online tenants in Microsoft 365. Then on October 2020 this was suddenly put on hold due to COVID and the impact it would have on business. Since then Microsoft have been turning off Basic Authentication on Tenants that have not been using it without impacting the end user. Now Microsoft have now set a new date, announcing that on the 1st October 2022, Microsoft will begin to permanently disable Basic Authentication in all tenants, regardless of usage.
So if you haven't already made the switch to Modern Authentication, now is the time to be proactive and start planning and implementing the change in a coordinated tested method before Microsoft makes the change for you.