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Creating an on-site Exchange to back up 365?

Anonymous
2025-06-03T10:56:02+00:00

Hi, we've got a small-medium size client with 365 who wants to create a "local backup" where if the online 365 goes down, they could just change MX records or something and keep on sending & receiving mail until Microsoft resolves their end. Apparently 365 outages have happened to them often enough to ask for this. My boss is having me to set up a local AD + Exchange virtual server and creating the users with an exported list from their 365 so we can use Entra to connect them all. The more I think about it, the more I believe it can't be done as the client's asking for, but just wanna double-check with the pros since I'm no certified MS engineer, and see if there's any supported way to do this (even if it's paying a 3rd party service).

Moving from original location: Microsoft 365 and Office / Other / Unknown / Other

Microsoft 365 and Office | Install, redeem, activate | For business | Other

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  1. Anonymous
    2025-06-04T04:43:38+00:00

    Hi F. Pelayo,

    Good day to you. Thank you for posting on Microsoft Community.

    Based on my knowledge, typically, hybrid deployments are designed for migrating to the cloud, not syncing mailbox data from the cloud to on-prem. Microsoft doesn’t offer a native method to continuously replicate mailbox data from Exchange Online to an on-prem Exchange server. So, even if you set up a local AD and Exchange VM and sync users via Entra, the mailboxes themselves wouldn’t be mirrored or usable in a failover scenario without significant manual intervention and risk of data inconsistency.

    In addition, a domain is only connected to a specific email provider. If you want to use a third-party email provider as a backup, your email service with this domain in Microsoft will be stopped. This is because MX records can only point to one destination at a time.

    As a forum moderator, I have limited access to backend tools and cannot provide deep technical validation for complex hybrid or continuity setups. I recommend you raise a ticket to Azure team in Entra Admin Center for more details about Entra Connect. Sign in to Microsoft Entra. They’ll be able to assess your client’s environment and provide guidance on whether any supported architecture or third-party solution could meet your needs. This would be a more efficient way in handling the case and confirm your information for you.

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    Note: only user have admin role is able to access Entra Admin portal and raise the ticket to Azure team.

    Thank you for your patience and understanding. I look forward to your response.

    Sincerely,

    Nam-D - MSFT | Microsoft Community Support Specialist.

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  1. Anonymous
    2025-06-08T23:33:33+00:00

    Hi F. Pelayo,

    If you still have further concerns, please feel free to let us know.

    Sincerely,

    Nam-D - MSFT | Microsoft Community Support Specialist.

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