Is your MigrationWiz migration failing because Exchange Online Basic Authentication is disabled in the tenant while your endpoint is still configured to use legacy credential authentication?

Microsoft has completed the deprecation of Exchange Online Basic Authentication across all tenants. If your MigrationWiz endpoints are still set to authenticate with Basic Auth against a tenant where Basic Auth is disabled, the migration will fail during authentication before any mailbox data is accessed.

MigrationWiz Modern Auth uses OAuth 2.0 via an Entra ID app registration in the source or destination tenant. In this model, the migration service account authenticates using the app registration client ID and client secret, rather than an SMTP username and password sent through Basic Auth.

At a high level, the app registration setup looks like this: create the application in Entra ID, grant Exchange Online API permissions at the application level with full access rights, add SharePoint API permissions if your project includes SPO or OneDrive workloads, generate a client secret, and then enter the client ID and secret into the MigrationWiz endpoint configuration.

Permission scope is workload-specific. Mailbox migrations require different Exchange permissions than OneDrive migrations require SharePoint permissions. If permissions are only partially granted, endpoint authentication may succeed but you will hit a 403 on the first item-level access attempt.

Have you confirmed that your MigrationWiz endpoint authentication method aligns with the Basic Auth deprecation status of both your source and destination tenants?

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