DataString.InvalidSmtpDomainName(Domain) when running the Office 365 hybrid Configuration Wizard.
In this post, I will show case how you can remove the following error when you tried to install the Office 365 Hybrid Configuration Wizard.
This error typically indicates that you have an Exchange server in your environment that is Offline or has not been decommissioned properly and is still listed in your environment.
You can verify all your Exchange Servers by running the following.
Get-ExchangeServer * |Fl
This will give you an output of all the Exchange Servers in your environment.
How to Resolve the Error?
To resolve the error, open ADSIEDIT and then connect to Configuration Container.
Then locate Exchange Administrative Group > Servers.
In the list of servers, you will see an Exchange Server which might have crashed or not properly decommissioned.
Right click on the Exchange Server that should not be in the Exchange Org and click delete.
Then click on Yes to confirm the deletion.
Then click on Yes to confirm that all objects in the container will be deleted.
You will notice that the Exchange Server container is no longer listed after the deletion.
If you have multiple Active Directory Site, force an Active Directory Replication.
Give the replication a minute or two and then rerun the Hybrid Configuration Wizard.
The Wizard will now be completed without giving you the DataString.InvalidSmtpDomainName(Domain). Error.
Hope this helps those who might have this error in the future.
Microsoft also posted about this error HERE.