smspva.com does exactly this. Phone verification (assuming you enforce non-VOIP and block certain countries) raises account creation costs by a decent amount,

smspva.com does exactly this. Phone verification (assuming you enforce non-VOIP and block certain countries) raises account creation costs by a decent amount, email verification not so much. The sad reality these days is that a T-Mobile phone number, a Comcast IP address and an outlook email doesn't mean someone isn't a bot, it means they spent a few dollars for a proxy and an some verification services. Which is why I think that behavioral indicators of botness and not just user agents and IP address whois are increasingly important in detection.