NSString* emailString = @"amigueloferreira@gmail.com";
    NSString *emailRegEx = @"[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,4}";
    NSPredicate *emailTest = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", emailRegEx];
    [emailTest evaluateWithObject:emailString]; //returns BOOL