The attempted operation is prohibited because it exceeds the list view threshold getting Quest Tool 6.16 SharePoint online

Thank you for posting in the Migrator for Notes to SharePoint (MNSP) forum.  We have seen this issue in a previous build however it may be possible something changed with SharePoint Online relating to this issue.  

Please open a support request so that we have one of our technical representatives investigate this in-depth and work with you towards a resolution of the issue. A hotfix is available for version 6.15 that you can request to resolve the issue while the issue with 6.16 is being investigated / worked on with the assistance of support. 

https://support.quest.com/create-service-request 

Regards,

Douglas Rain
Support Engineer
Quest | Support

This is a limitation imposed by SharePoint – a list (or DocLib) may not hold more than 5000 items to be displayed in the default view:

https://docs.microsoft.com/en-us/sharepoint/troubleshoot/lists-and-libraries/items-exceeds-list-view-threshold

A common workaround is using folders in SharePoint, and storing no more than 5000 items in one folder.

More elaborate solutions are based on indexing columns and changing the default view of a list using filters on indexed columns in a way that no more than 5000 items are displayed by default.


Regards,
Peter

Create a list first in SharePoint and then start migrating documents into it to resolve this issue or you can downgrade the version to 6.15 (it is working correctly on 6.15).