How to return mailboxes from Office365 ?

Андрей Михалевский 2,866 Reputation points

Hello. We had Exchange on-premise. We moved all the boxes to Office365 and removed Exchange on-premise.

How can I deploy Exchange locally again and get the mailboxes back?

Do I need to reconfigure the hybrid configuration ?

Microsoft Exchange Online Management
Microsoft Exchange Online Management
Microsoft Exchange Online: A Microsoft email and calendaring hosted service.Management: The act or process of organizing, handling, directing or controlling something.
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Exchange Server Management
Exchange Server Management
Exchange Server: A family of Microsoft client/server messaging and collaboration software.Management: The act or process of organizing, handling, directing or controlling something.
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Accepted answer
  1. Joyce Shen - MSFT 16,651 Reputation points

    Hi @Андрей Михалевский

    Yes, it's supported to re-add the on-prem server to your o365 and move mailboxes back.

    And for moving the mailboxes back, you need to reconfigure the hybrid environment.

    Do you still keep the original AD and on-prem server? If not, you could also deploy a new AD and Exchange server to finish the configuration. Only note that, we need to create the AD accounts manually before moving them back. And we need soft-match to match the on-premises users to the Office 365 user accounts.

    For more information about soft match (also called smtp match)
    How to use SMTP matching to match on-premises user accounts to Office 365 user accounts for directory synchronization
    Soft (SMTP) vs. Hard (immutableID) matching with Azure AD Connect
    Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.

    Then you will be able to perform the operation: Move mailbox from Exchange Online to on-premises

    For steps removing the hybrid and keep on-prem only, take a reference at the discussion in this thread: Roll back Hybrid Exchange to On-Premise Exchange
    WARNING: This is NOT supported by Microsoft, at all. Period. If there is a desire to do this, with support from Microsoft, you will need a support ticket and a Microsoft representative assisting you.

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