Update: The full timeline for retirement of Basic Authentication in Exchange Online is now published in Basic Authentication Deprecation in Exchange Online – September 2022 Update.
In February 2021...
Updated Sep 01, 2022
Version 19.0
Blog Post
Greg Taylor - EXCHANGE
Microsoft
MicrosoftQuiltersICT - as the first FAQ says, start here, or you wait for our MC posts to arrive. Start with the report would be my advice.
How do I know if my tenant is using Basic Auth?
Take a look at the Azure AD Sign-In log, as it can help identify ‘unexpected’ usage. We’re also going to start sending Message Center posts to tenant admins summarizing their usage (or lack of).
Lyle_Epstein SMTP is not being turned off if it's being used in your tenant. Please read the blog and FAQ's again.
Damon Villar As MikeCrowley said, we're not disabling any protocols, only specific auth types. They are not the same thing. MAPI(http, you are right, it's MAPI over HTTP, but we're just calling it MAPI in this case, but they are one and the same) is not being disabled. Basic Auth with MAPI is, but not OAuth. But yes, this change affects Outlook - but only if it is using Basic Auth with MAPI.