Office 365 migation from on-premise Exchange 2010 failed due to new mailbox created

Hello There,

We attempted to stage users to Office 365 from Exchange 2010 but the process failed due to Office 365 creating new mailbox after we initiate the license. It turned out that Office 365 will create a new mailbox if nothing in the object attribute indicates that there is already a mail-enabled object in the cloud during the licensing process. My question is what are these attributes to prevent Office 365 from creating new mailbox and recognize the mail-enabled object already exists??

Any reply is greatly appreciated.

Regards,

Lotusmail1

Franz Garcia