This article explains how to monitor your migration.

User List and Status

Your first tool to monitor your migration is the user list, where you can see the list of migrations and the status of each migration, and where you can sort them by status.
Monitoring

If an account displays an error, click on the user to display the root cause of the error.
Mail Error

Dashboard

Mail Dashboard

Click on the Errors tab.
You can get a list of mails in error for each user.