Web DAV must be used to export content from this mailbox.
This error occurs when MigrationWiz is attempting to access the content of a mailbox using EWS but that mailbox was previously migrated using WebDAV.
You can set
BypassHiddenFolderChecks=1in the Advanced Support Option of your user or project to allow the migration to continue using EWS.
Note: If this error occurs in the middle of the migration because you updated your Source environment, you will need to clean up the Destination, because the watermarking mechanism is different from WebDAV to EWS, and this will cause items to be duplicated.