After users are moved to BES12, the users exists in both BDS and UDS, if they have the same email address, that user must be merged into one BES 12 user. If a merged user has a field with a non-null value in BDS but null value in UDS (or vice versa), the non-null value will be used for the migrated BES 12 user. If a merged user has a field with a value that is different between BDS and UDS, the value from BDS will be used for the migrated BES 12 user. If a previously selected user is chosen to migrate, and the user (either its BDS or UDS half, or both, if it is a merged user) is not found when “Migrate” is clicked, entire migration will fail and a message that a user was not found is displayed to the admin.