docs: public static boolean isValidWithMXCheck (@Nullable final String sEmail)
    {
      // First check without MX
      if (!EmailAddressHelper.isValid (sEmail))
        return false;
  
      final String sUnifiedEmail = EmailAddressHelper.getUnifiedEmailAddress (sEmail);
  
      // MX record checking
      final int i = sUnifiedEmail.indexOf ('@');
      final String sHostName = sUnifiedEmail.substring (i + 1);
      return _hasMXRecord (sHostName);
    }