System.Web.HttpUnhandledException: Exception of type 'System.Web.HttpUnhandledException' was thrown. ---> System.Net.Mail.SmtpException: Transaction failed. The server response was: <unknown[10.16.3.15]>: Client host rejected: Access denied

<smtp from="ikke-svar@skien.kommune.no" deliveryMethod="Network">
        <network host="159.130.8.42" port="25" userName="" password="" defaultCredentials="false" />
      </smtp>