When Outlook clients don’t autoconfigure after a BitTitan cutover, the failure can look like a migration problem. Often it’s Autodiscover for the destination tenant not resolving correctly.

Outlook uses Exchange Online Autodiscover to find the right endpoint and build the MAPI profile. After cutover, that’s how it learns the mailbox now lives in the destination tenant. If Autodiscover for the destination domain doesn’t resolve properly, Outlook can’t make that change on its own.

The lookup follows a specific DNS chain that ends at the Microsoft-hosted Autodiscover endpoint. Custom Autodiscover CNAME records pointing to third-party filtering services or on-premises Exchange CAS servers can send Outlook to the wrong endpoint.

Before cutover, confirm the destination tenant domain’s Autodiscover resolves to the correct Exchange Online endpoint, and test it with the Microsoft Remote Connectivity Analyzer.

Have you validated Autodiscover resolution for the destination domain before your cutover date?

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