Migrate Exchange Hybrid Server to other domain

Iron Contributor

Hi, At a customer we have migrated almost all of the mailboxes from two different domains to One Office365 tenant. Now that we are almost done we are looking into the posibilities of migrating the Hybrid server to another AD domain. Is there anyone who has experience with this and can give me some global steps or recommendations on how to do this?


Currently we have 10 Exchange Cashub servers and 1 Hybrid server. This is represented in domain A. The Users are in Domain B (our new AD Domain) and had Linked mailboxes to the exchange environment in domain A. All the mailboxes have been moved towards Office 365.


The users are currently synced from Domain (mail resource domain) A and Domain B (New user domain) towards the Office 365 tenant. I hope someone can advise me. For additional info please let me know

11 Replies
From a hybrid perspective - do you plan to leave any users or resources in Exchange on-premises? Or is the hybrid "server" purely for GUI management of Exchange Online users?
The Hybrid server will only be used to manage users in Exchange online. All users will be moved to Office 365

Hi Jerry,


If you just want to manage the users in Exchange Online and you want to keep Exchange Hybrid, you have to keep only one hybrid server connected to your Office 365.


You have to migrate the rest of the mailboxes that you need to migrate to Office 365 than Install other Exchange on the other domain an turn it hybrid. Note: You have to change your configuration of your AD Connect to acomplish that.

Status updat: we now have migrated everybody over to Exchange online.

So the situation now is


All mailboxes are in Office 365

Users are synced from 2 domains (DomainA (mailresource domain) and DomainB (userresource domain).

The hybrid server is still in domain A.


The question now is can we and how do we move the Hybrid server over From DomainA to DomainB. And does this impact our AzureAd Connect which is syncing from DomainA and DomainB

best response confirmed by Jerry Meyer (Iron Contributor)

Hi Jerry,


You have to Setup a new Installation of Exchange Server on Domain B.


After instalation of the new Exchange Setup, you have to Uninstall Exchange on Domain A and then Run the AD Connect Again to discover the new Exchange and after that changes you Have to setup a new Hybrid Configuration Wizard on Exchange on Domain B.

Thanks for your response we will start testing this next week in our test lab :) i will keep you posted.

Keep in mind that you have to export the MailboxGUID from Exchange Online to your migrated user accounts in domain b in order to offboard users (if required).

And, to avoid downtime, change your MX and Autodiscover record to Office 365, migrate everything to domain b, switch records (if required) back to your new on-premise infrastructure.

Test lab is a good approch :) Make sure your your identities will be matched correctly and everything will work.

Goedemiddag Jerry. We have the same situation at a customer and  just posted a question on this as well at


Can you have a look and maybe have an answer on this? Thanks!

Status update,


Currently we have reduced our Exchange farm to a much smaller environment from 15 Exchange server to 2 exchange servers. One Hybrid and One Cashub.


We are now testing a couple of scenarios in our test lab.  Currently we have a succesfull move but it takes a lot of scripting before everything works. For instance the MSexchangerecepientdetails needs to be copied over to the user in the new domain.


I will get into more details when we are further with testing

Hi Jerry,

I am soon to face the same task..

So we have an on-prem server and all users are remote-mailbox users (according to it) so O365 online users and they are sync'd from domain A using AADSYNC currently.

We probably also do have a few local security groups, mail contacts and the like in on-prem environment.

The active directory domain, users have been synchronized using ADMT to domain B in preparation for domain migration (for the users) ..

So now I have to plan adding an on-prem exchange presence in Domain B also.. again to allow for management of certain attributes that Exchange online doesn't make easy..

So I'm looking for a fool proof/simple ! way to do this.. and would be keen to hear of any difficulties you had.

I do not have a test lab.. and so must tread carefully in this task..

any help/direction would be wonderful.




I have already send you a personal message. I don't know if it allowed but i have worked out this case on my personal blog. I am not sure if it is allowed to share this here. But you can finde the 2 project within the urls bellow.


Azure AD connect migration


Exchange Hybrid Migration


If you have any question please let me know. Also feedback on the blogposts are very welcome :)