RESOLUTION:
MNE does not migrate a Custom Attribute to a Standard Attribute in use
such as “Subject”, “Location”..etc
MNE is designed to migrate some Standard Attributes, and can also migrate
Custom Attributes to UNUSED Attributes in Exchange.
MNE does not filter the duplicated properties
(for example checking for two Subjects: one Standard Subject, one Custom Subject).
I this case, there will be two Subject Attributes in Exchange.