Add additional authoritative E-Mail Domain in between Transition/Migration project Exchange 20XX > 2016 (Onpremise), on which side to add?

Question

Add additional authoritative E-Mail Domain in between Transition/Migration project Exchange 20XX > 2016 (Onpremise), on which side to add?**

Hello,

Customer has:

DAG/Exchange 2010 (60% users are still on 2010 because of MDM)
DAG/Exchange 2016 (40% users migrated over)

• E-Mail Domain will not change
• Not all users need the new E-Mail Domains (Just a few)

Wants: To add a new fresh add. E-Mail Domain now during the migration period (Enterprise with Archive Solution/MDM etc. bigger project)
We never added an additional authoritative new E-Mail Domain during the migration phase. We always did that before or after the project.

Does the customer need to add the new E-Mail Domain on?

a) Exchange 2010 Side

or on the:

b) Exchange 2016 Side

We understand that this an Organization Wide settings. The question is just where to add without running into hidden problems.

We are aware of address-policys and customer has dynamic based on ADS-attributes. Only a few Mailboxes need the new E-Mail domain.

This is such a thing will you are to do and afterwards you get into trouble at some point we have a feeling.

Thank you for any help in this rather silly question ;-)

Greetings from Switzerland

Answer 1

Hi @switzerland ,

Based on my understanding and test, you can add the additional authoritative domain on either side.

As is mentioned in this document, accepted domains can be added using either EAC or EMS. From the user interface in EAC, there isn't any option to choose a certain server. And when it comes to the New-AcceptedDomain cmdlet, according to this article, the cmdlet doesn't have a parameter to specify a particular server. So when a new accepted domain is created, it's actually added for the entire organization:

I've also tested in my coexistence lab and noticed that, no matter where I added the accepted domain, the new created domain can be seen and managed from both sides, for example:

1. A new accepted domain is created from the EAC for Exchange 2016:
   
2. Check the EMC on Exchange 2010 and can see and edit the new created accepted domain:
   
3. And vice versa, if the new accepted domain in created from Exchange 2010 EMC, it can be seen and managed from Exchange 2016 as well:
   
   

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