To ensure your CRM users don’t receive any email notifications during the migration process, ask them to check the notification settings for their profiles.
To turn off email notifications, go to Settings > Notifications.
On the notification tab, find the Assign section, and make sure that “Email” is unchecked:
Unchecking the email checkbox ensures that no notifications will be emailed to your users.
Warning: Don’t forget to switch your email notifications back to ON after the migration progress is completed.