E-mails can be customised within the personalise messages section in the dashboard. You can customise all of the three e-mails which are sent to your customer:
At the time of signup/login- OTP sent over mail
When the order is placed
When the order is shipped



Detailed instructions to customise e-mails and other messages are available in this article.

Make sure you save the changes once they have been made. Copy and paste the default message in the custom message box to revert it to default.