keep on-premise exchange server after hybrid move migration to exchange online

dirkdigs 921 Reputation points
2021-09-11T03:21:19.59+00:00

Hello I've inherited a network where they have mailboxes in exchange online (cloud) and also have on-prem exchange 2016 server still running . (no mailboxes left on-prem. )
MX records are Exchange online. I'm not sure why the on-prem server is still running . Is there any best practices I can do in order to determine whether or not it's still actually required for anything? Do i need to analyze the hybrid connector somehow? Should I just power it off? What is the best practice in this scenario.

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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Microsoft Exchange Hybrid Management
Microsoft Exchange Hybrid Management
Microsoft Exchange: Microsoft messaging and collaboration software.Hybrid Management: Organizing, handling, directing or controlling hybrid deployments.
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  1. Vasil Michev 99,936 Reputation points MVP
    2021-09-11T06:39:18.303+00:00

    Any scenario that involves dirsync, that is syncing your on-premises objects to Office 365, requires you keep at least one Exchange box for maintenance purposes. Read here: https://learn.microsoft.com/en-us/exchange/decommission-on-premises-exchange

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  2. dirkdigs 921 Reputation points
    2021-09-11T22:21:07.167+00:00

    what are you talking about? i have many customers without any exchange server and they are using DirSync.

    Maybe i need to clarify that the hybrid was only used to move mailboxes to Exchange online and that has been completed.
    DirSync is only required for the password sync.

    Please explain,

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  3. KyleXu-MSFT 26,236 Reputation points
    2021-09-13T06:55:00.26+00:00

    @dirkdigs

    In a organization without Exchange on-premises, you could sync AD account to AAD, then assign license to enable mailbox.

    In a hybrid mode, if you uninstall Exchange on-premises without remove AAD Connect. This action will remove mail attributes from local AD, then sync AAD, which will broken the Exchange online mailbox.

    So, you need to follow the Scenario one to disable directory synchronization and remove Exchange on-premises. If you want to using AAD Connect, you could recreate it to sync AAD account to local AD after removing Exchange on-premises.


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  4. dirkdigs 921 Reputation points
    2021-09-15T13:04:50.92+00:00

    I have moved many customers to Exchange online and powered off the exchange server.
    Also we continue to use AAD Connect the whole time.

    In a hybrid mode, if you uninstall Exchange on-premises without remove AAD Connect. This action will remove mail attributes from local AD, then sync AAD, which will broken the Exchange online mailbox.

    I have not seen this to be honest . All my Customer which have been moved to cloud (Exchange Online) are working fine.

    Can you be more specific on which mail attributes you are talking about?

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