Mailbox Migration to Exchange Online, Strange error…

Recently I tried to do some mailbox migration tests between my on-premises Exchange infrastructure and Exchange Online in Office 365. The mailbox move/migration should be the simple part on any migration project as you spend all the time ensuring the other parts of the solution are correct. However I queued a new move request recently as I needed a new mailbox in Exchange Online to test some settings in SharePoint Online… The move started, but it failed with the following:

After a number of checks and trying the migrations again still with no joy, I thought I’d remove the user/object from Office 365. Prior to removing the object I connected to Exchange Online via PowerShell and ran:

Get-MailUser –Identity “Affected user email” | FL *GUID*, Ident*

I then moved the users AD Object in my local Active Directory to an OU that was not being synchronised to Azure AD, and performed a full sync. Once the sync had completed I confirmed the user object was no longer in Azure AD, then moved the AD Object back to synchronised OU and perform another sync. After the sync had completed I re-ran the previous PowerShell cmdlet:

So by performing these actions I can see that I managed to get a new object GUID for the this mail user. I then performed a new mailbox migration to Exchange Online which completed successfully.

I will add that my home lab does get a load of abuse, where I test different exchange scenarios, but I do this so I know how to fix issues etc. its very possible I caused this error within my lab when I was doing previous disaster recovery tests. So there is a very good chance that you may never see this error.

I know that this process can be very long especially if your Directory Synchronisation has a lot of objects, so I’ll continue to look if there is another way to resolve this.

Disclaimer: All scripts and other PowerShell references on this blog are offered "as is" with no warranty.  While these scripts are tested and working in my test environment, it is recommended that you test these scripts in your own test environment before using in any production environment.