The best way for you to do this would be to view the Audit Log Report in ODME. This can be done by following these steps:
1) From the On Demand Migration for Email (ODME) Plans Dashboard, click on "Reports" in the lower right-hand corner of the screen
2) Click on "Audit Log" on the left-hand pane
3) Click on "Source Mailbox" to sort the list by source mailbox
4) Review the "Result" column to find if the migration was Successful or Unsuccessful
5) As another option, they can click on the "Download Additional Details" box in the lower right-hand corner of the Audit Log screen to download the report (with a bit more data) into a CSV file. They can then look at the "Final Migration State" field to see if a migration was a Success or not.