Importing your emails from an existing email service like Yahoo or Gmail creates 'copies' or backup of every email in your Helm account. This means that all data imported over continues to exist in the original account.
Without any further action on your part, the old account will continue to receive mail and store all existing mail. The import process does not delete any messages nor delete your account.
Please note: New emails coming in to the old account will not automatically be imported to your Helm account.
To cut ties with your old email services and take back control of your data, view the full recommended process for Importing & Migrating Email here.