During an On Demand Migration (ODM) mail migration, the following behaviors are observed:
External emails are forwarded to the target mailbox successfully, but internal emails (sent from unmigrated source users) are not delivered.
Attempting a Mailbox Switch on the test account fails with the error:
Error Mailbox Switch The object is not found in Office 365
This error typically occurs when the target user object's metadata, GUID, or mailbox attributes have changed in Microsoft 365, causing the ODM backend mapping state to lose synchronization with the target tenant object.
Ensure the Migration Admin account has all necessary Exchange permissions assigned in the target tenant. Refer to KB 250237 for specific role assignments.
In the ODM portal, select the affected user account(s).
Click Refresh Accounts to force ODM to re-query Microsoft 365 and update its cached account metadata.
Once the refresh task completes, re-attempt the Mailbox Switch task.
If refreshing the account does not resolve the error:
Run the Match task on the affected user(s) and select the option to Clear Existing Matches.
Once the clearing task completes, run the Match task again (using your standard matching rule or a mapping file).
Verify that the target User Principal Name (UPN) is mapped correctly in the user list.
Run an incremental Mail Migration task.
Attempt the Mailbox Switch task again.
If clearing and re-matching the account still fails to resolve the issue:
Delete the affected user account from the ODM workspace interface.
Run a new Discovery task against the source and target tenants.
Perform the Match task on the rediscovered account.
Run the Mail Migration task.
Execute the Mailbox Switch task.
