So here is an interesting one.
We know Office 365 groups are a hybrid Exchange Online / SharePoint Online thing.
When you create an Office 365 Group, it creates an MSOLGroup and a UnifiedGroup object, that you can access using Windows Powershell (Get-MsolGroup / Get-UnifiedGrou).
Any email addresses that are set as Primary on the unified group, replicate up to the MSOLGroup object.
Now, you can remove them from the unified group, but they will NEVER be removed the MSOLGroup object. Try it ;-)
This means, if you need to do say a Tenant to Tenant migration, and the default msoldomain is a vanity domain, all office 365 groups will have the vanity domain as primary and you cannot remove it!
The only fix, is to delete the group! -or- raise a call with Microsoft and have your engineer engage with the Microsoft Online Domain Services Backend team (Azure AD) to remove them for you.
Just received this:
We are excited to announce a new version of Migration Manager for AD 8.14 is now available for download.
Look what's new:
The highest priority matching rule with the UserPrincipalName target matching attribute will be automatically configured for each new migration pair. Such matching rule can be manually added to existing migration pairs and collections using Migration Manager for AD (Microsoft Office 365) console.
8.14 can be installed on Microsoft Windows Server 2016.
Support for processing of Microsoft Windows Server 2016 using Resource Updating Manager.
Support for migration to Windows 2016 AD including: Migrating objects to Windows 2016 AD, Synchronizing objects with Windows 2016 AD in both directions, Synchronizing passwords with Windows 2016 AD, Migrating SID-History to Windows 2016 AD and Migrating computers to Windows 2016 AD.
Migration Manager for AD 8.12 is now in limited support. To determine the current support phase of your product, please refer to the Migration Manager for AD life cycle table.
Be sure to check out the Migration Manager for AD Product Support page to find solution articles, tips and tricks, tutorials, documentation, notifications, life cycle tables, training, and a product user forum.
Important Notice: Due to our recent divestiture from Dell Technologies, we are required to retire any Dell branded software from our Support Portal. This means that all software downloads and technical documentation for Migration Manager for AD prior to version 8.14 will be removed from the Support Portal after November 1, 2017. Please download any older versions now that you may need for your future use.