The online store sends automated messages to the customer while the order is being processed. You can see those messages on the Messages sent section on the order page. By clicking the message's name, you can see its contents.
Sending messages manually
You can send a message manually to the customer by clicking New message. Next, choose a template for the message. There is a list of automated messages such as Order confirmation or if you want an empty template, choose Message related to order. That template includes only a greeting (Hello customer's first name) and your message, of course.
Next, write the message in the Message field. If necessary, preview the message by clicking Preview under the message field.
When the message is ready, click Send.
You can edit the automated messages and their settings by following the instructions in the Automated emails article.