Microsoft will permanently disable basic auth in all tenants beginning Oct 1, 2022, regardless of usage, except for SMTP Auth.

Keep this in mind & disable legacy auth for all apps.

You can quickly determine if legacy auth is in use with these 4 steps by Gregor Reimling

https://twitter.com/GregorReimling/status/1560569029542150144/photo/1

Basic Authentication Deprecation in Exchange Online – May 2022 Update

In about 150 days from today, we’re going to start to turn off Basic Auth for specific protocols in Exchange Online for those customers still using it.

Since we announced the October 1, 2022 deadline last year we’ve seen great progress from customers and partners as they move their clients and apps from basic to Modern Authentication. Since there are a lot of customers still using Basic Auth, we wanted to re-state the scope and implications of this change, and to answer some of the common questions we get.

https://techcommunity.microsoft.com/t5/exchange-team-blog/basic-authentication-deprecation-in-exchange-online-may-2022/ba-p/3301866?WT.mc_id=AZ-MVP-5003249