As mentioned, you can't stop it. The frustrating part is, you still get spammed 2 years later for something you searched for. There are 2 things you can do. Create a new account with something like a Hotmail or Gmail address, where you never have to check the email address again, and search using that account. If you find something you want to buy, then you can use you main account to buy.
You could also stay logged out to search. If you find something you want to buy, you can then log in to buy it.
