Cutover Migration Merging With Existing Objects

Question

We have an Office 365 org with thousands of objects (mailboxes, contacts and groups).  They have various domains, but none have the domain of xxx.org.  We have initiated a cutover migration with the Exchange 2010 server for xxx.org and, during the migration, similar objects are being merged.  For instance, there was already an Office 365 distribution group called *** Email address is removed for privacy *** and there was an on-premise distribution group called *** Email address is removed for privacy ***.  The cutover migration has merged the members of both and changed the default SMTP address to *** Email address is removed for privacy ***.  In another instance, we had an Office 365 mailbox called *** Email address is removed for privacy *** and an on-premise mailbox called *** Email address is removed for privacy ***.  Again, the cutover migration has merged these and changed the default SMTP address to *** Email address is removed for privacy ***.

This is a disaster since there are thousands of objects and we have no way to tell which ones this has happened to and which ones it hasn't.  Furthermore, all articles I can find and all of our previous experiences indicate that trying to migrate where an existing object is in place will cause that object to fail.

The on-premise server is Exchange 2010 Enterprise, fully patched.  There is no dirsync, no adfs or anything like that.  This is a straight-up, vanilla cutover migration to an Office 365 organization with thousands of existing objects and several domains, none of which were previously xxx.org.

How can we prevent this?  How can we revert these damaging changes?  This isn't the normal behavior, is it?  Any help would be appreciated, this is causing a major disruption for our existing users.

Answer 1

Hi Tom,

I’m sorry I cannot understand your requirement completely. Could you please give us an example for this?

If possible, please also give us the result Neo Yu mentioned via Private Message.

Thanks for your understanding.

Jason Jiang

Answer 2

Neo, actually, I'm a little unsure how to proceed.  Basically, out of our 1600+ objects (880+ as part of the current cutover), I know of one mailbox that this has happened to and one group.  The problem with the group is that it merged existing members and new ones.  They are not part of the same company (just part of the same O365 org).  For the mailbox, one of the IT staff renamed it and changed the primary SMTP back to the old address, so it doesn't accurately reflect the results of the botched cutover.  I can export the info for that user/mailbox, but it won't show the proper settings since the cloud mailbox already existed and the on-premise one is untouched.  Does that make sense?  I'm looking for a way to find out which objects (groups, contacts, mailboxes) were affected by this so that I can run the above commands against those objects to gather more info.  Any ideas?

Answer 3

Neo, apologies for the delay.  I am gathering the info right now and will PM them to you.  Thank you.

Answer 4

Hi Tom,

Have you checked my previous post? Let us know if you get any updates.

Answer 5

Hi Tom,

This is not what we commonly see, to further check it, can you please provide the following information?

On both the on-premises Exchange server and Exchange Online, run the following PowerShell cmdlet for the migrated mailbox and copy the entire results (the two).

Get-Mailbox –Identity <user mailbox> | FL

Get-recipient –Identity <user name> | FL

Get-User –Identity <user name> | FL

I have sent you a private message to request the NDR above. Please refer to the following steps to view the private message: 

• Go to the Your details section on the right side of the community site.

• Click Private messages.

• Click the subject title of the response to read the message.

• You can reply by using the form that displayed.

• Click Submit Reply.

For the revert part, I’d like to confirm if you have check the recipient details in the migrated mailbox’s inbox. If the recipients are different, we can use the Outlook client to move all the mail items with the same recipient into one folder using the Outlook client side inbox rule, then export/archive the messages from the account to a new one.

However if the recipients can’t be identified, then sorry to let you know that we may not be able to revert the change back. Your understanding is appreciated.