Decommisioning old Exchange 2013-2016 when running hybrid Exchange ?

Question

Hi All,

Based on the article: https://learn.microsoft.com/en-us/Exchange/manage-hybrid-exchange-recipients-with-management-tools#will-this-work-for-me I am trying to install 1x Exchange Server 2019 2019 VM on Windows Server 2019, and then shut it down to minimize the attack vector.

This is my existing setup throughout my single forest AD Domain:

All of the above servers just running as mailbox servers and all of the mailboxes have been migrated to Exchange Online (Hybrid Exchange & Azure AD).

What's the procedure to uninstall or decommission the above existing Exchange Servers?
Can I install 1x Exchange 2019 on Windows Server 2019 VM in Azure and then shut it down?

Any help and suggestion would be greatly appreciated.

Thanks in advance.

Answer 1

@EnterpriseArchitect

From this blog, we can know that from Exchange Server 2019 CU12, we could shut down the last Exchange server, then use Exchange Management Tools to manage recipient.

Before that:

You need to install Exchange 2019 CU12 to coexist with Exchange 2016 and Exchange 2013 first.

Then migrate Exchange 2013/2016 hosted arbitration mailboxes to Exchange 2019. You could use the command below to check which server arbitration mailboxes hosted:

Get-Mailbox -Arbitration  

After that, change DNS record to make Exchange 2019 as internet facing server and rerun HCW to choose Exchange 2019 as hybrid server.

Now, you could shut down Exchange 2013 and Exchange 2016 to check whether there exist issues with the new configuration. If there doesn't exist issue, you will could uninstall Exchange 2013 and Exchange 2016.

In this way, there will only exist Exchange 2019 in your local AD. If you want to shut down Exchange 2019, you need to install Exchange Management tools on a domain-joined workstation.

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