fat_fingers

https://github.com/charliepark/fat_fingers

Makes sure users don't accidentally create an account for the wrong e-mail address. Because 'gmial' isn't actually what they meant to type. Similarly, 'yaho.com', or the strange-but-true '.c0m'. Not even making that one up. If you're concerned about false-positives, it's super-easy to check. There's only a single method. Also, it's fully-tested.