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Office 365 is the favorite destination of the majority of business organizations when they think about a suitable cloud platform. It has become a dominant player in the cloud business and businesses are migrating their data at a rapid speed. However, there are multiple precautions which you should take care while migrating the data; otherwise, there can be some unwanted errors.

In this article, we will go through one significant error which does not even let the migration started. The error is following:

The request failed. The remote server returned an error: (401) Unauthorized.

Instant Solution

To migrate your Office 365/Microsoft 365 data securely, try Kernel Office 365 Migration tool. It is a quick and accurate tool for all Office 365 Migration task.

If you are facing this kind of error, then there may be multiple reasons behind this issue

  1. The user ID is different than the UPN (User Principal Name).

    If the Office 365 account which you are using is different from the UPN from the Active Directory, then you will have to face the error.

  2. MFA (Multi-Factor Authentication) is enabled for Office 365.

    If the Office 365 has multi-factor authentication enabled for the account, this it is not easy for a manual method to access the mailbox easily.

  3. The Username and Password have incorrect spelling.

    The spelling of the username and password of the Office 365 is not correct.

  4. The domain of Office 365 is not registered with the DNS of the Microsoft.

    Many times, the user creates an Office 365 account and try to start the migration instantly. Then the error may occur, because the domain of the Office 365 may not be registered with the Microsoft DNS.

    If you are facing this error, then you may try to use the following solutions to rectify the problem:

    1. Update the Administrator credentials.
    2. Edit the Migration Endpoint in the Exchange Admin Center. Try to check complete detail of the batch migration and edit the information.
    3. If the Password of the Administrator account is too complicated, then reset it.
    4. Assign the Global Administrator credentials to the Office 365 account.
    5. Choose a different Office 365 account for the migration.

Professional Solution

After making all the appropriate changes in the Office 365 account, the error should be removed, and the migration should also be smooth. But if you still are facing the same error due to UPN settings and there is no manual method to solve the problem, then use a professional tool which can bypass all the technicalities and perform the migration on your terms. Kernel Office 365 Migration is the best-suited migration software which can access the email ID along with the UPN ID and complete the migration. Here is the brief procedure for Office 365 data migration –

  1. After successful installation, run the software and click the Add button to select the source.
    select the source
  2. Input the credentials of the source account and click the Add button. Single Mailbox/Office 365 Group option is selected by default. To migrate multiple mailboxes, select the second option.
    Input the credentials
  3. The tool will enlist all the accounts associated with the Administrator account. You can select/deselect the account quickly. Click Add.
    Click Add
  4. In the next windows, you need to map both source and destination account. Click the Set Filter and Migrate button.
    Set Filter and Migrate button
  5. The following window will let you select the desired type of item like Mailbox, Public Folder, and Archive Mailbox. You can make your selection from the drop-down menu and then click the Migrate button.
    select the desired type of item
  6. The Filter Selection window has some best-suited filters options to select only the essential data to migrate and leave the rest.
    Date Filter – Input a date range.
    Item Type Filter – Check various options among Email, Journal, Task, Contacts, Calendar/Appointment.
    Exclude Deleted Folders – Stop the deleted folders from migration
    Exclude empty folder – Stop empty folders from migration.
    Save all hierarchy in a new folder – Provide a name of the folder, and all the data will be saved in the folder.
    Set operation timeout – Set the time limit for the migration of each item.
    Skip previously migrated items – Stop already migrated items from migration.
    Finally, click I am OK, Start Migration.
    click I am OK, Start Migration
  7. After a successful migration, the tool will provide you a message that migration is complete. Click OK.
    Click OK
  8. To get a comprehensive migration report, click the option Save report to CSV.
    click the option Save report to CSV

After completing the migration procedure, click OK.


When you are using this KernelApps tool, you will not have to face errors like 401 – Unauthorized Access. It is a flexible tool which supports the Office 365 environment and reduces the network complexities. For much assistance, you can contact the technical team which is available to you 24*7.