Hi,
You can use, modify or add custom e-mail templates in the
E-mail templates section in Site Manager -> Development.
Also, you can configure whether the notification should be sent when particular order status is reached (
Order status configuration). You can also add custom status - shipped and send the notification for this status too.
In the e-mail templates, you can use macro expressions to customize the content of the e-mail.
Best regards,
Juraj Ondrus