Running the Mailbox Enable process in Migrator for Notes to Exchange (MNE) with Exchange 2016 CU4 as a target fails with:
ERROR: [7430-1-54-80004005]Unable to restore directory entry
 Unspecified error
Issue that has been identified as a Defect with the ID 674824 is resolved in MNE 126.96.36.199.
Latest MNE Hotfix can be downloaded from here