To edit the look and feel of the email notifications that are sent out, go to the Notifications tab and scroll down to 'Customer Emails'. Click on one of the emails and click on 'Edit Template' to get started:
If you wish to simply edit the text of the email, click into the inline editor and press Ctrl + F (Cmd + F for Mac users) and search for the text you are trying to edit. In the example below, I am going to change 'Your return request has been submitted' to 'Rest easy, we're working on your request.':
You can do the same for any other text edits. If you wish to change the styling, kindly note that the template editor only accepts inline CSS. As for other positioning, you may refer to the email variables to ensure that your emails are set the way you like.