Cause of error
During an Export to PST migration, the 10GB default size for a PST file has been exceeded. This limit is set because of the resource load on the server during export process of the migration.
On the Advanced Options page, in the Support Options dialog box, enter:
Important: This advanced option should be used with the understanding that the User's migration may not operate properly, and should be a last resort because of the effect this can have on server resources.
The property value <GB size> is the new maximum PST gigabyte size for the migration. This number should match the PST file size.
If it is necessary to control size, PST files can be recreated using a subset of folders from Outlook, as well as using available online tools.
Note: This option is only applicable to the Export to PST migration scenario, if you're migrating from a PST file to a mailbox, this will not work.