When migrating Mailin-DB, you need to escalate "Manager/Author" ACL rights in Notes to Full Access permission to Shared mailbox.
A new parameter has been implemented in MNE 4.15.2 and later:
[Notes]
ElevateMailInDBEditorAclToFullAccess=
When ElevateMailInDBEditorAclToFullAccess=1, the Data Migration Wizard elevates Notes' Manager, Designer, and Editor access levels for the Mail-In database which have "Delete documents" rights to Full Access permission in the Exchange Shared mailbox. By default (0), this feature is disabled.
See the MNE Program Parameters Reference Guide for additional details.
