I am currently working in an environment where we are migrating from Forest A to Forest B . The purpose of this migration is to transition to a new domain, and using the rendom tool is not an option. Current Environment: Mailboxes: Previously hosted on on-premises Exchange, but they have now been migrated to Exchange Online . We still have the on-premises Exchange server in place for mail flow. Hybrid Configuration: The Hybrid Configuration Wizard (HCW) has been enabled, and we have Hybrid Azure AD Connect configured with hybrid enabled settings in the source environment. Email Applications: Some applications are currently using the on-premises Exchange server to send emails. Migration Plan: AD Migration: We have finalized the timelines for the Active Directory migration and plan to use Active Directory Migration Tool (ADMT) . Azure AD Connect: After migrating all objects to the destination forest, we plan to disable AD synchronization in the source environment. Instead of importing the Azure AD Connect settings from the source, we are considering re-creating the configuration for the Azure AD Connect tool in the new forest, using mS-DS-ConsistencyGuid as the source anchor. Mail Flow: Once we have established mail flow with the Exchange mailboxes authenticating against the new forest's Active Directory, we intend to decommission the source environment's Exchange server. Request for Advice: I would like to receive suggestions on how to effectively plan this migration to avoid any disruption in mail flow during the transition. Specifically, I am concerned about: Ensuring continuous mail flow while migrating objects to the new forest. Configuring Azure AD Connect in the new environment without causing synchronization issues. Any additional considerations or best practices to follow during this migration process. Thank you for your assistance!

Hello, @ Ashutosh Kumar , Welcome to the Microsoft Q&A platform! Based on your description, I understand that you have a comprehensive plan for migrating from Forest A to Forest B and would like some advice on how to ensure a smooth migration. Migrating Active Directory (AD) and ensuring uninterrupted mail flow can be a complex process, here are some tips to help you make a smooth transition. About how to ensure continuous mail flow while migrating objects to the new forest, the following steps are recommended: 1.Properly configure the Hybrid Configuration Wizard (HCW) in both forests, which will help maintain mail flow during migration. 2.Ensure that the mail flow between Exchange Online and the local Exchange server is configured correctly by sending and receiving test emails. If you want to configuring Azure AD Connect in the new environment without causing synchronization issues, here are some things to keep in mind: 1.When setting up Azure AD Connect in a new forest, use mS-DS-ConsistencyGuid as the source anchor point, which will help maintain consistency and avoid synchronization issues. 2.Use Azure AD Connect in staging mode in the new forest, which allows you to verify configuration and synchronization without affecting the production environment. Once all objects are migrated to the new forest, disable AD synchronization in the source environment to prevent any conflicts. As for additional considerations and practices to follow during this migration process, please refer to the following points: 1.Before the formal migration, set up a test environment to simulate the migration process, identify possible problems, and verify the effectiveness of the solution. 2.Ensure that you have up-to-date backups of all data prior to migration and have an emergency recovery plan in place to prevent data loss due to unexpected issues. 3.Implement a mail flow monitoring tool during the migration process to monitor the transmission of emails in real time and identify and resolve transmission failures in a timely manner. 4.Regularly review Exchange and Azure AD Connect logs to identify potential errors or warnings that can provide important troubleshooting information. If the answer is helpful, please click " Accept Answer " and kindly upvote it. If you have extra questions about this answer, please click " Comment ". Thank you for your support and understanding. Best Wishes, Alex Zhang

Decommission Exchange Server in Cross-Forest AD migration (mailboxes in Exchange Online)

Accepted answer

Alex Zhang-MSFT 3,155 Reputation points Microsoft Vendor

2024-10-08T08:35:38.93+00:00

Hello, @Ashutosh Kumar,

Welcome to the Microsoft Q&A platform!

Based on your description, I understand that you have a comprehensive plan for migrating from Forest A to Forest B and would like some advice on how to ensure a smooth migration.

Migrating Active Directory (AD) and ensuring uninterrupted mail flow can be a complex process, here are some tips to help you make a smooth transition.

About how to ensure continuous mail flow while migrating objects to the new forest, the following steps are recommended:

1.Properly configure the Hybrid Configuration Wizard (HCW) in both forests, which will help maintain mail flow during migration.

2.Ensure that the mail flow between Exchange Online and the local Exchange server is configured correctly by sending and receiving test emails.

If you want to configuring Azure AD Connect in the new environment without causing synchronization issues, here are some things to keep in mind:

1.When setting up Azure AD Connect in a new forest, use mS-DS-ConsistencyGuid as the source anchor point, which will help maintain consistency and avoid synchronization issues.

2.Use Azure AD Connect in staging mode in the new forest, which allows you to verify configuration and synchronization without affecting the production environment. Once all objects are migrated to the new forest, disable AD synchronization in the source environment to prevent any conflicts.

As for additional considerations and practices to follow during this migration process, please refer to the following points:

1.Before the formal migration, set up a test environment to simulate the migration process, identify possible problems, and verify the effectiveness of the solution.

2.Ensure that you have up-to-date backups of all data prior to migration and have an emergency recovery plan in place to prevent data loss due to unexpected issues.

3.Implement a mail flow monitoring tool during the migration process to monitor the transmission of emails in real time and identify and resolve transmission failures in a timely manner.

4.Regularly review Exchange and Azure AD Connect logs to identify potential errors or warnings that can provide important troubleshooting information.

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".

Thank you for your support and understanding.

Best Wishes,

Alex Zhang
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1 person found this answer helpful.
Ashutosh Kumar 20 Reputation points

2024-10-08T20:47:14.3333333+00:00

Hello Alex,

Thanks for your answer.

I would like to highlight, that we do not want to keep Exchange on-prem in the new environment and we would like to set up the new environment as a cloud-only (for mailboxes). The user objects would still be syncing from the local AD.

Is there a way to achieve this?

I was thinking to:

Install Exchange on-prem in the destination environment, to expand the schema of the new forest.

Once installation is done, we will then uninstall exchange server from the AD as we do not want to keep on-prem exchange.

Then perform the migration of user objects through ADMT.

Set AD Sync up in the destination forest, in staging mode to check the behavior of some of the migrated objects and their mail flow.

Once things appear good, we will plan to migrate the rest of the object from source AD to destination AD (cross-forest).

Please let me know your thoughts on this approach, and if there's anything which I can do differently.

Alex Zhang-MSFT 3,155 Reputation points Microsoft Vendor

2024-10-09T03:22:16.4233333+00:00

Hello, @Ashutosh Kumar,

Thank you for your prompt and patient reply.

I have understood your requirement that you do not want to keep Exchange local in your new environment and want to set your new environment as cloud only (for mailboxes). Your approach is generally sound. I will then respond and make suggestions on the four points you mentioned.

Extending the architecture for New Forest is necessary to extend the architecture. At a minimum, you will need to install Exchange Management Tools to prepare for the Office 365 hybrid configuration.

According to Microsoft official document, at least one Exchange server should be left for management, it can be deactivated, but it is not recommended to uninstall it. It is not recommended to uninstall it, because after deleting it, if there are problems with AD properties, then managing local mailboxes will become complicated. It is time consuming and labor intensive to manage local servers, but it is good for management. If you feel that the local server is completely useless and you won't manage AD properties in the future, then you can uninstall the Exchange server from AD according to How and when to decommission your on-premises Exchange servers in a hybrid deployment | Microsoft Learn after the architecture extension is completed.

Migrating user objects via ADMT is critical for migrating user accounts to the new AD forest. Ensure that you migrate all necessary properties, including those related to mail and test with a small group of users before proceeding with a full migration.

Configuring Azure AD Connect staging mode allows you to verify the synchronization process without disrupting your production environment. This step is critical to ensure that migrated objects and their mail streams are working properly. After a successful staging mode check, you can proceed with a complete object migration and fully test the mail flow and other features.

As for adjustments I suggest you make, please consider the following points.

Install Exchange in the target environment to prepare the architecture and setup the hybrid configuration tools. Retain a minimal hybrid environment to ensure smooth administration and supportability.

Migrate users using ADMT and verify synchronization with Azure AD Connect in staging mode. Ensure full testing of migrated objects and mail flows.

Plan for long-term Exchange attribute management and consider retaining an Exchange server with minimal roles if necessary.

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment". This will make answer searching in the forum easier and be beneficial to other community members as well.

Thank you for your support and understanding.

Best Wishes,

Alex Zhang

Alex Zhang-MSFT 3,155 Reputation points Microsoft Vendor

2024-10-11T08:17:52.55+00:00

Hello, @Ashutosh Kumar,

If the answer is helpful please click on ACCEPT ANSWER as it could help other members of the Microsoft Q&A community who have similar questions and are looking for solutions.

Best Wishes,

Alex Zhang

Alex Zhang-MSFT 3,155 Reputation points Microsoft Vendor

2024-10-15T02:01:45.19+00:00

Hello, @Ashutosh Kumar,

If an answer has been helpful, please consider accepting the answer to help increase visibility of this question for other members of the Microsoft Q&A community. If not, please let us know what is still needed in the comments so the question can be answered. Thank you for helping to improve Microsoft Q&A!

Best Wishes,

Alex Zhang

Ashutosh Kumar 20 Reputation points

2024-10-15T21:42:22.1633333+00:00

Hello Alex,

Thanks for your assistance on this.

I am in the process of applying the proposed solution in my target environment. I will keep you posted on this thread regarding the progress and the final results.

Thanks again.

Regards,

Ash

Ashutosh Kumar 20 Reputation points

2024-10-16T12:41:38.1633333+00:00

Hello Alex,

I had a query regarding the proposed solution.
If I choose to install Exchange Management Tools, I understand that I will have to manage my recipients using EMS.

Based on the scenario I explained above, after installing the EMS, do I have to configure HCW as well?
Please note, we do not end up maintaining a hybrid deployment, and we want to become cloud-only with the mailboxes on Exchange Online.
We are OK to use Exchange Management Tools, for managing the exchange related attributes in our AD environment.

Waiting for your response.

BR,
Ash

Alex Zhang-MSFT 3,155 Reputation points Microsoft Vendor

2024-10-17T02:42:57.39+00:00

Hello, @Ashutosh Kumar,

Thank you for your prompt reply.

According to your description, if you choose to install EMS and manage your recipients by using EMS, you do not necessarily have to configure the HCW when you are aiming to become cloud-only with mailboxes on Exchange Online and do not wish to maintain a hybrid deployment because HCW is typically used to configure and manage hybrid deployments.Here's a simplified version of how you could proceed.

1.Install Exchange Management Tools: This will allow you to manage Exchange-related attributes for your users in the on-premises AD environment.

2.Sync AD with Azure AD: Ensure that your on-premises AD is synchronized with Azure AD using Azure AD Connect. This way, any changes to Exchange attributes in on-premises AD will be reflected in Exchange Online.

3.Manage Recipients with EMS: Use the Exchange Management Shell (EMS) to manage recipient properties and other Exchange-related attributes in your on-premises AD. These changes will be synced to Exchange Online.

4.Migrate Mailboxes to Exchange Online: If you haven't already, move all your mailboxes to Exchange Online. Once they are all in the cloud, you can decommission the on-premises Exchange servers if you're confident you no longer need them for administrative tasks.

One point you need to remember is that, even if you're operating in a cloud-only mode, you may want to retain the Exchange Management Tools to handle attributes that are specific to Exchange and may not be manageable directly through Azure AD or Exchange Online.

If an answer has been helpful, please consider accepting the answer to help increase visibility of this question for other members of the Microsoft Q&A community. If not, please let us know what is still needed in the comments so the question can be answered. Thank you for helping to improve Microsoft Q&A!

Best Wishes,

Alex Zhang

Ashutosh Kumar 20 Reputation points

2024-10-17T06:30:19.58+00:00

Hey Alex,

Thanks for the quick reply.

There's a thing that has been bothering me since the day I have installed Exchange Management Tools on the destination server.
I understood the concept that we need AT LEAST Exchange Management Tools for managing the Exchange related attributes, and to expand the schema in the destination AD to accommodate the Exchange related attributes (that would be copied from the source environment during the migration through ADMT).

However, after I installed Exchange Management Tools in the destination, I see that the schema has expanded but when I launch Exchange Management Shell, it asks me which Exchange server I would like to connect to (the FQDN of the Exch server). Now since we do not have any active Exchange server in the destination, I can't get past this screen on the EMS.

I believe I would be able to manage all the Exchange related attributes from the Users and Computers console. Right?

Please let me know if I need to do something different.

BR,
Ash

Alex Zhang-MSFT 3,155 Reputation points Microsoft Vendor

2024-10-18T05:36:13.1866667+00:00

Hello, @Ashutosh Kumar,

I understand your situation. When you install the Exchange Management Tools, it primarily provides you with administrative interfaces like the Exchange Management Shell (EMS) and the Exchange admin center (EAC), which typically need to connect to an Exchange server to function properly. Since you don't have an active Exchange server in the destination environment, connecting via EMS directly isn't possible.

For managing Exchange-related attributes without an active Exchange server, you can indeed use the Active Directory Users and Computers (ADUC) console. The Exchange Management Tools extend the AD schema, allowing you to manage Exchange attributes directly from ADUC.

Here are a few steps to ensure you’re on the right track:

1.Verify Schema Update: Ensure that the schema update was successful. You can use the Get-ADObject cmdlet in PowerShell to check for the presence of Exchange attributes.

2.Use Active Directory Users and Computers (ADUC):

a. Open the ADUC console.

b. Navigate to the desired user or object whose Exchange attributes you want to modify.

c. Right-click the user, select "Properties," and navigate to the "Attribute Editor" tab. If you don’t see it, you may need to enable "Advanced Features" in ADUC (View > Advanced Features).

If you need to perform more advanced management tasks, you might consider setting up a minimal Exchange server in the destination environment, even if it’s just for management purposes. This can provide you with full access to the Exchange Management Shell and other tools.

If the answer is helpful please click on ACCEPT ANSWER as it could help other members of the Microsoft Q&A community who have similar questions and are looking for solutions.

Thank you for your support and understanding.

Best Wishes,

Alex Zhang

Alex Zhang-MSFT 3,155 Reputation points Microsoft Vendor

2024-10-23T01:27:17.23+00:00

Hello, @Ashutosh Kumar,

If the answer is helpful please click on ACCEPT ANSWER as it could help other members of the Microsoft Q&A community who have similar questions and are looking for solutions.

Best Wishes,

Alex Zhang

Alex Zhang-MSFT 3,155 Reputation points Microsoft Vendor

2024-10-25T02:39:08.01+00:00

Hello, @Ashutosh Kumar,

If an answer has been helpful, please consider accepting the answer to help increase visibility of this question for other members of the Microsoft Q&A community. If not, please let us know what is still needed in the comments so the question can be answered. Thank you for helping to improve Microsoft Q&A!

Best Wishes,

Alex Zhang
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Decommission Exchange Server in Cross-Forest AD migration (mailboxes in Exchange Online)

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