Hi @Anonymous
Agree with the reply above from Andy, this thread discussed the similar question as yours and some points we need to notice
Deploy Exchange 2013 in multiple domain scenario
You need to prepare the domain to accept the exchange organization into it. (Note you can't have a seperate exchange org, it will be conencted to the existing org, but with different user scope)
Make sure to follow the full preparation steps as in for the first exchange deployment.
The final step to get Active Directory ready for Exchange is to prepare each of the Active Directory domains where Exchange will be installed or where mail-enabled users will be located. This step creates additional containers and security groups, and sets permissions so that Exchange can access them.
The account you use needs permissions depending on when the domain was created:
- Domain created after PrepareAD was run If the domain was created after you ran the PrepareAD command in step 2 above, then the account you use needs to 1) be a member of the Organization Management role group and 2) be a member of the Domain Admins group in the domain you want to prepare.
- Wait until Active Directory has replicated the changes made in step 2 to all of your domain controllers. If you don't, you might get an error when you try to prepare the domain.
When you're ready, do the following to prepare an individual domain in your Active Directory forest for Exchange.
- Open a Windows Command Prompt window and go to where you downloaded the Exchange installation files.
- Run the following command. Include the FQDN of the domain you want to prepare. If you want to prepare the domain you're running the command in, you don't have to include the FQDN.
Setup.exe /PrepareDomain:<FQDN of the domain you want to prepare> /IAcceptExchangeServerLicenseTerms
- Repeat the steps for each Active Directory domain where you'll install an Exchange server or where mail-enabled users will be located.
Note If you are joining an existing Exchange site, the account that you use to log on must have the following permissions to access the Exchange Server directory:
- Exchange must recognize the site services account name and password.
- The Exchange Server site naming context for the Exchange Server site you want to join.
- Admin role on the Exchange Server configuration naming context for the Exchange Server site that you want to join.
- A two-way trust is required between the domain where you are installing Exchange and the domain where the Exchange Server computer exists.
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