Starting October 1, Microsoft will begin to randomize tenants and disable basic authentication access for MAPI, RPC, Offline Address Book (OAB), Exchange Web Services (EWS), POP, IMAP, Exchange ActiveSync (EAS), and Remote PowerShell.
As you know, SMTP AUTH will not be affected by the changes made.
On the day of the change, Microsoft will notify each tenant through the Service Status Dashboard.
If you’re not ready to make these changes, You can do a One-Time Re-Enablement one last time as decided by Microsoft.
For all the details; Basic Authentication Deprecation in Exchange Online – September 2022 Update
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