If your scenario matches the scenario above, then the following steps will allow you to make use of this new "O365 to O365 with domain name transfer" feature:
1.) Use On Demand Migration for Email to migrate the content of mailboxes to the target Office 365 tenant. We would suggest using the default tenant alias (firstname.lastname@example.org) for both the source and target email address when adding users to a migration plan. This will allow for an additional "final pass" migration after the primary SMTP domain is "cutover" to the new Office 365 tenant.
For detailed information on CPUU configuration, usage, and limitations, see Updating Outlook Client Profiles in the On Demand Migration for Email User Guide.
2.) Create a temporary service mailbox in both the source and target Office 365 tenants. These accounts will be used to process profiles, for example fetching Autodiscover information from source and target tenants. These accounts do not require any special administrative rights and can be "normal user" accounts. For more details on further limiting the rights of these "cpuu service accounts", see How to Limit Account Rights.
3.) Use the CPUU configuration wizard to create the CPUU.ini file as described below.
4.) Copy the entire CPUU installation directory:
C:\Program Files (x86)\Quest\Client Profile Updating Utility
To a location where all users will be able to execute it from, such as a file share.
Note: In order to gather log files from CPUU all users will need write access to the file share that CPUU_Update.bat is being ran from.
5.) Configure the CPUU_Update.bat so that it is run automatically on user logon, such as through a Windows Group Policy (for example) as a user logon script.
6.) Transfer the domain name to the target Office 365 tenant. After this moment, the users cannot use their existing Outlook profiles without processing them by CPUU.
Note: After profile processing it might take some time for Outlook to resume the normal and expected behavior.
7.) Run a "final pass" migration with ODME to ensure all items have been migrated.
8.) After all user profiles are switched to the target, remove the group policy set in Step 5.
How to create the CPUU.ini file
1.) Start CPUU configuration wizard.
2.) Select O365 to O365 with domain name transfer (ODME only – not applicable for MMEX) migration scenario. Click Next.
3.) Provide credentials for service mailboxes.
Important: CPUU service account user names should follow this syntax:
4.) Add domain names that will be kept after migration. Only profiles with email addresses from these domains will be processed by CPUU.