El Jannah has recently began sending emails to survey people who have signed up with them, but not bought anything through the app in a while.
This email seems to be targeted, and upon completion of the survey, they ask you if you want to be rewarded a $20 voucher. After picking yes, you will receive a new email with the voucher that can either be used in store, or online.
The voucher is $20 off $30.
Got this on 2 accounts. Last purchase was May.