In an Exchange Server environment, when you perform an eDiscovery search and then export the results through the eDiscovery PST Export Tool, the export never finishes and you receive the following error message:
Export failed with error: Export failed with error type: 'Unknown'. Details: Value cannot be null.
Parameter name: key.
This issue occurs when the Item property has a Null value when results are exported.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
Learn about the terminology that Microsoft uses to describe software updates.