Hi,
I can provide you 750,000 USA email ids right away (though, not sure how many of these will be from Houston, TX). All these email ids are valid and of registered users on one of my USA based client's website. My client also don't mind selling me these emails leads as I am the one who has developed his website & managing his website & database from last 5 years now.
Also, please note that all these are users have good credit score history as well.
Hope to hear from you soon...
Thanks & Kind Regards,
Anu