What should we do with mailboxes that are in the NonExistent text file from the Time Zone Extraction process?

Q: what should we do with users (mailboxes) that are in the NonExistent text file from the Time Zone Extraction process?

A: NonExistent.txt file contains Milaboxes for which tool could not able to gather time zone information. So you ca copy thier Legacy DNs to Mailboxes_x.txt and add appropriate Time Zone Information and Exchange Server name and reabse them. Make sure you follow correct format in mailboxes_x.txt file.