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BugZero found this defect 740 days ago.
This article provides information on actions that must be taken to ensure Veeam Backup for Microsoft 365 will continue to function after the Basic Authentication Deprecation in Exchange Online.
Organizations added to Veeam Backup for Microsoft 365 using either Basic Authentication or Modern Authentication with Legacy Protocols, must be switched to Modern App-Only Authentication.
Microsoft Article: Basic Authentication Deprecation in Exchange Online – September 2022 Update Microsoft Documentation: Migrate your public folders to Microsoft 365 Groups in Exchange Online