There is no security in knowing whether you qualify up until they see your credit reports and for that they need your permission. You can opt out from these mail offers for 5 years and opt back in anytime. This may help you from tempting to inquire on your credit causing to decrease credit scores.
However, if you feel like you would want to receive these offers to see what are your options are to create credit then you may request to opt-in as well.
Overall companies exchange your personal information (Purchase $) in benefit to selling you their products.