This is Oswald, a Guru here at Shopify!
The shipping notifications are sent automatically upon fulfillment of the order unless you manually uncheck the box "Send notification email to customer" during the process.
If you are using an app to fulfill your orders, make sure that within its settings the customer notification emails are enabled for the shipments.
To verify if the email was sent to the customer, just go to your Shopify Admin > Orders, click the order you wish to check, scroll down to the "timeline" section and you should see something like the following.
If the email was not set, under the fulfillments section, click the "more" box, click "edit tracking", make sure the send shipping notification box is checked, and click save. This should trigger the shipping notification to be sent to the customer.
Hope the information above helps! If you have any other questions, feel free to reach out to the Guru team. :)
Oswald | Shopify Guru
Make sure you have enabled the box "Send notification email to customer". Once this is done, the shipping notifications are sent automatically upon order fulfillment. To verify if the email was sent to the customer, just go to your Shopify Admin > Orders section. You can see tracking email notification details.
Shopify automatically sends the "Order Confirmed" and "Order Shipped" notifications for all the orders.
But, the "Order out for delivery" and "Shipment delivered" notifications will only be sent out when you fulfill orders that have tracking information from USPS, UPS, FedEx, and Canada Post.
For other carriers, you will have to use an app like Shipment Tracking & Notify app, which will help you send tracking notifications to your customers. The app also allows you to have an integrated tracking lookup page, from where your customers can track their orders.