Oh no! It pains us to see you go. You may refer below steps!
Using ShopBack web:
Kindly submit your email address here, and you will be unsubscribed in 3-5 days.
Using ShopBack app:
Go to Account, scroll down to the bottom, and tap on Newsletter & Deal Info as per screenshot below:
Once tapped on Newsletter & Deal Info, you may choose to receive or not receive it by tapping on the slider bar: