Depends on how you're going to be verifying them. If it's an SMTP method, good luck. Most places will not open port 25 period, whether you say you'll be a good boy with it or not. Lol. If it's a web based method though, any decent proxies should work. There's a ton of good sellers in the marketplace. If it is an SMTP method, it'll be a little tricky to find, and very, very expensive once you do. In that case you may as well send, cuz you'll be paying as if you were. Good luck though and have a good one.