2. Go to Domain List, find your domain and click on the caret to expand the list of the associated services (make sure All Products is selected in the top right corner):
3. Look for your Private Email subscription in the list and select Manage from the drop-down list next to it:
NOTE: Once the old mailbox is deleted, emails, contacts, and calendars associated with it, will be deleted from the server with no way to restore them. If you wish to keep the emails, firstly, it is required to back them up so you can restore them in the new mailbox later.
4. Scroll down to the mailbox management section, and select Remove from the drop-down menu next to your mailbox:
5. Now, you have a free slot for creating the new mailbox with the new name. Click on the Create Mailbox button:
6. Insert the mailbox name you wish to have, its password and mailbox storage, then click Save Changes: