there are three ways to solve this issue, you can ignore the promotional email, you can unsubscribe, or you can log in and change the email to the one that you rarely use, we all have disposable emails, it only proves that you are still not cured and a mere mention of gambling site will get you irritated, a person that is cured of gambling will not get agitated or irritated from this issue, based on your post you still hate Stake.com for the many loss you incurred.
Recovering from addiction is a very difficult process. In this case, Stake.com knew perfectly well that the situation was very difficult since the user himself asked to close the account. In my opinion, Stake.com knew that a user is addicted to gambling and continued to send him promotional offers, it was very inappropriate. In my opinion, such a person should be helped, not made difficult in this way.