To setup automatic notification e-mails to be sent to your customers when you ship their order, just follow the steps below.
Head to your Account Settings (the gear icon in the upper right).
Next, select Selling Channels and then Store Setup from the sidebar on the left.
Find the store for which you want to have e-mails sent, then select Edit. Click on the Notifications sub-tab.
To send a Shipment Notification Email, simply make sure that you have your desired template selected.
Please Note: If there is no field available to choose an e-mail template, then we will be unable to send e-mail confirmations for that store.
Click Save Changes at the bottom of the page.
If you do not want ShipStation automatically email your customers, remove the email template selection by selecting the "(Don't send email)" option. When this option is selected, ShipStation will request that your eCommerce platform notify your customers when a label is created.