^[a-zA-Z0-9]+((\.|-|_)[a-zA-Z0-9!#$%&\'*+-/=?^_`{|}~]+)*([-_])*@[a-zA-Z0-9][a-zA-Z0-9-]{0,61}[a-zA-Z0-9]((\.|-)[a-zA-Z0-9][a-zA-Z0-9-]{0,61}[a-zA-Z0-9])*\.[a-zA-Z]{2,6}$