Active directory user migration accross domain with Exchange Server

Question

Dear Experts,

Need your advise one below-

We have one of our customer running domain abc.com, for whom the acquisition is done by xyz.com. They are running abc.com with on-primise exchange 2013 and AD is on Windows 2012 R2. Now they want to migrate all users from abc.com to xyz.com with minimal or no downtime. What the best way forward here (any 3rd party paid tool with can be used).

Our objective -

1. Migrate all users with exchange mailbox to xyz.com domain
2. We want to ultimately upgrade to Windows 2019 based DCs
3. Exchange also needs to be upgraded to Exchange 2019

We read of internet about not doing any migration to across forest with Exchange as its not supported. Need your expert opinion and advise.

Thanks for the help in advance.
Regs,

Answer 1

Hi @Ajay Kumar

We have one of our customer running domain abc.com, for whom the acquisition is done by xyz.com.

Did you mean the current AD domain is abc.com, while the SMTP domain to send/receive emails is xyz.com?
And they are considering moving cross forest to AD domain xyz.com?

If I misunderstood the scenario, please feel free to correct me.

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We read of internet about not doing any migration to across forest with Exchange as its not supported.

Here is a link about cross-forest migration: Exchange 2010 Cross-Forest Mailbox Moves
It is about Exchange 2010 but should also work as the general steps are similar.

In short, the steps would be:

1. run prepare-moverequest.ps1 script in the target forest to prepare for the mailbox move
2. use ADMT tool to migrate the AD account to the target forest
3. move the mailbox to the target forest

Since I suppose you are using the same SMTP domain, you may setup internal relay domain in the source forest to relay messages to the target forest once the mailbox has been migrated.

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Another method without third-party tools would be migrating by export/import pst files.
The general steps would be:

1. export the mailboxes in the source forest to pst files
2. use ADMT to migrate AD accounts to target forest
3. create new mailboxes for these users
4. import the pst files into these new mailboxes

How to export mailbox contents to pst file: Procedures for mailbox exports to .pst files in Exchange Server
How to import pst files into mailbox: Procedures for mailbox imports from .pst files in Exchange Server

To reduce downtime, configuring internal relay domain to ensure mail flow is also recommended.

In addition, if you have ADMT installed before the Exchange server is installed, when using ADMT to migrate the user accounts, the Exchange related attributes would not be excluded as expected (By default these attributes are supposed to migrated by the prepare-moverequest.ps1 script, if they are migrated by ADMT, it would cause problems).
And you may need to reinstall ADMT or manually exclude the attributes.

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Answer 2

Hi there,

Your first step would be to complete all the prerequisites for migrating to Windows 2019 DC from Windows Server 2012.

Here are some quick steps to do the migration with less downtime.

Set up a new server using Windows Server 2019.
Join the new server to your existing Active Directory domain.
Install the Active Directory Domain Services role.
Promote the new server to a domain controller.

Here are some articles which might be really useful for your carrying on these steps properly.

Exchange Cross-forest migration when source and target domain use the same email address
https://learn.microsoft.com/en-us/answers/questions/572404/exchange-cross-forest-migration-when-source-and-ta.html
Upgrade Active Directory Windows server 2012 R2 to Windows server 2019
https://learn.microsoft.com/en-us/answers/questions/384793/upgrade-active-directory-windows-server-2012-r2-to.html

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