When you try to send an email message to a user whose mailbox is being migrated to Microsoft Office 365 Dedicated/ITAR (vNext), you receive the following non-delivery report (NDR):
NDR 532 5.3.2 STOREDRV.Deliver: Missing or bad mailbox Database property.
This issue typically occurs very rarely and for a very short time period. There is a short window at the end of the migration when Active Directory Domain Services (AD DS) is being updated. This error may occur during that period.
If the NDR occurs one or two times during the migration, this is expected and no action is required, except that you must resend the email message.