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Hi Microsoft experts.
I have a concern like the article here https://practical365.com/removing-premises-exchange-servers-migrating-office-365/, but I don't know if Microsoft has a solution so far for decommissioning on-premises Exchange but still keeping on-premises AD syncing users to M365?
My plan is after migrating all mailboxes to M365 I would like to completely decommission on-premise Exchange Server but still retain the on-premises Active Directory for other requirements, directory synchronization and password hash sync so that users have a single set of credentials to remember for authenticating to Office 365 cloud services.
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Hi, @Parker Tran
Based on your description, I understand that you still retain ADFS for users after migrating your mailbox to M365.
Luckily, it is achievable. But you cannot completely decommission Exchange servers from your on-premises environment, you can decommission most of them, leaving a couple of servers for user management and those servers that can run on virtual machines.
Scenario 2 in the following article can meet your needs. How and when to decommission your on-premises Exchange servers in a hybrid deployment | Microsoft Learn
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My organization does not use ADFS. We have a Domain Controller and installed Azure AD Connector on that for password hash sync. The user on AD still be synced to Azure AD and other services of M365.
Exchanger Server on-premise with 1TB capacity and it's a virtual machine. I don't want to keep it anymore. What will happen if I decommission it?
As all mailboxes on-premise have migrated to M365. Why do we have to keep this? It's a waste of resources
In the article https://learn.microsoft.com/en-us/exchange/decommission-on-premises-exchange#scenario-two does not have a scenario that we need
Hi, @Parker Tran
Sorry for not being able to reply in time.
From your description, I understand that you have at least one domain controller and one on-premises Exchange server.
If you want to keep directory synchronization and password synchronization, it is recommended that you do not completely decommission the Exchange server on-premises, leaving at least one for user management and running it on a virtual machine.
If you completely decommission the on-premises Exchange server, you cannot make changes to the mailbox object in Exchange Online because the source of authority is defined as on-premises.
Since you have migrated all your mailboxes to Exchange Online, if you have multiple Exchange on-premises servers from a resource conservation perspective, you can retire most of them and leave only one for user management.
In addition, if you don't require the use of EAC for management of recipients in your hybrid organization, you can remove the last Exchange Server on-premises, while keeping the directory synchronization.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
The meaning of "EAC" is Exchange Admin Center but you are mentioning "EAC" of Exchange Server of "EAC" of Exchange Online. Currently, I'm only using Exchange Admin Online to manage the mailboxes
duplicated with the above ansers
Hi, @Parker Tran
From your reply to Amit Singh's comment, I very much agree with your idea that you want to optimize the system and save resources.
The main problem is directory synchronization and password synchronization, not that all mailboxes have been migrated to the cloud.
If you migrate your mailboxes to the cloud and don't need to manage users from on-premises, or need directory synchronization or password synchronization, you can safely remove your on-premises servers, just like scenario one mentioned in the article.
However, this is not the case, and you need to continue to keep directory synchronization or password synchronization after the migration is complete, so it is recommended that you do not completely decommission all Exchange server on-premises. For the sake of management and resource conservation, the best practice is to keep one Exchange server on-premises. Or optionally, install Exchange 2019 management tools on a server and turn off the Exchange server on-premises. More information can be found Removing Your Last Exchange Server FAQ - Microsoft Community Hub
As you said, managing on-premises servers can be a waste of resources, but since sources of authority are defined on-premises, keeping a portion of the servers on-premises reduces the likelihood of catastrophic failures from a security standpoint.
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Let me clarify this a bit. Currently, include the following servers in my organization
For now, I would like to completely decommission Exchange Server 2013.
The synchronization process still happens normally. When have a new employee, I just create an account in AD and let it sync to M365, and assign Exchange Online license to it to create a mailbox. Will there be any effects later if I decommission the Exchange Server?
Hi, @Parker Tran
Glad to hear from you.
While it may seem like a no-brainer, the decision to get rid of the on-premises Exchange servers is not simple and definitely not trivial.
Even if all mailboxes have been migrated to Exchange Online, decommissioning an on-premises Exchange Server has some implications, especially when it comes to the management of email attributes.
Here are some things to keep in mind:
1.Decommissioning an on-premises Exchange server without performing the appropriate retirement steps may disrupt the hybrid configuration and synchronization process. This may cause issues with user mailboxes and other settings syncing correctly between on-premises AD and Azure AD.
2.If the last Exchange server is removed, you cannot make changes to the mailbox object in Exchange Online because the source of authority is defined as on-premises.
3.Without an on-premises Exchange server, you might face challenges managing mail attributes such as proxy addresses, mail-related properties, and distribution groups. It will lose the convenient and fast management interface EMS.
4.Some administrative tasks that are typically performed via the on-prem Exchange Server might become more tedious or might not be possible once the server is decommissioned.
To safely decommission Exchange Server, consider the following steps:
1.Make sure there are no dependencies: Verify that all mail flows and relays have been moved to the cloud or other servers.
2.DNS records: Update or delete any DNS records pointing to the on-premises Exchange Server.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Hi, @Parker Tran
Is there any update on this thread? If the issue has been resolved, please mark the helpful replies as answers, this will make answer searching in the forum easier and be beneficial to other community members as well. Thanks for your understanding.
Hi @Xintao Qiao-MSFT
I have shut down the Exchange 2013 and observing further. We can stop discussing here, thank you everyone !
Hi, @Parker Tran
If there are additional issues after the Exchange 2013 server is retired, you can continue to participate in the discussion.
You can also click "Accept Answer" and vote yes to help someone who has the same problem as you, thank you for your understanding and support.
I think you are talking about Exchange Hybrid Configuration between your on-premises Exchange Server and Office 365.
After migrating all mailboxes to Office 365 you can completely decommission on-premises Exchange Server but still retain the on-premises Active Directory for other requirements.
Once you have migrated all mailboxes to Office 365, remove all mail flow connectors and uninstall Exchange Server.
With the help of Azure AD Connect, keep the on-premises AD synchronized with Azure AD.
After this, by Office 365 admin center or through EMS, you can manage all mail-related tasks.
Hi Amit
This is exactly what I'm concerned about. According to the article https://learn.microsoft.com/en-gb/exchange/decommission-on-premises-exchange?redirectedfrom=MSDN
Microsoft recommends keeping at least Exchange Server because there are attributes that can only be managed by Exchange on-premise.
I've already migrated all email to the cloud, but we still need to maintain an on-premises Exchange server. This is illogical and complex, as I have to manage both environments and it wastes resources.
Yes, it can be frustrating to manage both. Microsoft recommends keeping at least one Exchange Server because of several Exchange-specific attributes and also compliance and security purposes. Let’s see if there is any update on this by Microsoft.
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If you are looking for a migration between On-premises Exchange server and Office 365, then I would suggest you use a professional solution named Weeom Exchange to Office 365 Migration (Weeom Exchange Server Suite) Software.