Mailbox is present in both Office 365 Legacy Dedicated and vNext after license is applied

Scenario 1: Keep the legacy mailbox, and deprovision the vNext mailbox

1. Export the contents of the vNext mailbox. To do this, follow these steps:
   1. Generate an eDiscovery search. To do this, see In-Place eDiscovery.
   2. Export the eDiscovery search to PST. To do this, see Export eDiscovery search results to a PST file.
2. Remove the license for the customer's vNext mailbox. To do this, use one of the following methods:
   • Office365 Portal: Assign or remove licenses for Office 365 for business
   • PowerShell: Remove licenses from user accounts with Office 365 PowerShell
   • If using group-based licensing:
   1. Remove the user from the group
      • If Dynamic Group is used, ensure user does not match criteria so that user can be removed. This may require modification of the rules, which must be done carefully as it can affect all other members of the group.
3. Previously, Microsoft had to clear msExchPreviousHomeMDBSL and msExchPreviousMailboxGuid Active Directory attributes from the vNext user object. This can now be done through self-service. Please refer to the following article to perform this step:
   
   Permanently Clear Previous Mailbox Info
4. Provide the PST file to the end user to import by using the Outlook client. To do this, see Import email, contacts, and calendar from an Outlook .pst file.