Switch to Modern App-Only Authentication
To continue protecting the Organization's Microsoft 365 environment after Basic Authentication is deprecated, the authentication method used by Veeam Backup for Microsoft 365 to connect to the environment must be set to Modern authentication.
To change the organization's authentication within Veeam Backup for Microsoft 365:
- Select the Organization and Click Edit
- On the "Microsoft 365 connection settings" page of the wizard, select the option for "Modern authentication"
Do not select the option labeled "Allow for using legacy authentication protocols"
- Proceed through the rest of the wizard steps.
Reference: Select Azure Region and Authentication Method
When using Modern App-Only Authentication, Veeam Backup for Microsoft 365 utilizes custom scripting to process web parts of SharePoint/OneDrive sites. To prevent issues processing WebParts, review and implement the solution documented in KB4091.