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A cloud-based mailbox wasn't found for...

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We are performing a migration from Exchange 2003 to 365, some accounts are copying over just fine, some are returning this error:


A cloud-based mailbox wasn't found for "" Create a mailbox for "" in the cloud-based organization and try again.




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  • Hi WidePoint2012,

    I understand that you are performing an email migration from Exchange 2003 to Office 365 and encounter this error "A cloud-based mailbox wasn't found for ‘’ Create a mailbox for ‘’ in the cloud-based organization and try again".

    Are you performing a Cutover Exchange migration or Staged Exchange migration?

    If you are performing a Staged Exchange migration, this issue can be caused if the user account hasn’t been created in Office 365. Given this situation, please check if the user account " " is shown in Microsoft Online Portal, if not, please create the user account and try to run the migration again.

    Larry He

  • We're doing a cutover migration. Do I need to create the user accounts first with the Directory Sync before doing a cutover? The instructions said not to

  • Hi WidePoint2012,

    For doing a cutover migration, there is a help article.

    Larry He

    0 out of 1 people found this post helpful.

  • You guys keep pointing me to the same article over and over for our issues, we've been through multiple times and still no resolution!

  • Hello,

    Don't run DirSync for a cutover migration.

    I'm wondering what the migration status is for this.  Using a Remote Exchange PowerShell session, run the following command and give us the results:

    Get-MigrationStatus | FL

  • We're not running DirSync for the cutover

    The migration keeps failing on multiple accounts with different errors each time, some are generic, some are not.

    I'm not familiar with remote powershell, so I am not able to run that.

  • Hi WidePoint2012,

    I understand that we may meet some errors during running a cutover exchange migration.
    Based on current situation, I suggest you to stop a migration, remove these mailboxes which were migrated to Office 365 and run the cutover exchange migration again.

    Additionally, there are several new cmdlets that are available to manage migration batches in Exchange Online R6:

    Remove-MigrationBatch -Identity "Name of Migration Batch"(To remove an existing email migration batch from the queue)
    Get-MigrationUserStatistics (Retrieve the status for each single user in a migration batch).
    Set-MigrationBatch (Configure several settings on an existing migration batch).
    Remove-MigrationBatch (Removes any migration batch object from the email migration batch queue).

    For how to Connect Windows PowerShell to Office 365, please refer to this article:

    Besides, there is a help article about cutover exchange Migration:

    Larry He

  • I have opened a ticket with support and they are recommending we do a staged migration since they can't figure out what's wrong.

  • Hi WidePoint2012,


    Does the ticket you opend solve this problem?

    If you need more help, please feel free to contact us.

    Larry He