There are SMTP addresses that are perfectly valid, non-local and yet does not contain '@'. But in practice that could be probably ignored. But if you want to v

There are SMTP addresses that are perfectly valid, non-local and yet does not contain '@'. But in practice that could be probably ignored. But if you want to verify email address, then going with must contain '@' is probably one of the more reasonable routes (you should probably also ban few characters like newlines and ';').