C# SMTP client using CDO

The following code utilize the CDO service of Windows OS to send an email. In my research CDO SMTP client can only support SSL/TLS connection type for using SSL. If you want to use START TLS connection type, C# SmtpClient class can support it.

/// <summary>
    /// Send an electronic message using the Collaboration Data Objects (CDO).
    /// </summary>
    /// <remarks>http://support.microsoft.com/kb/310212</remarks>
private void SendEmailWithCDO()
                var settings = ViewModel;

                CDO.Message message = new CDO.Message();
                CDO.IConfiguration configuration = message.Configuration;
                ADODB.Fields fields = configuration.Fields;

                // Set configuration.
                // sendusing:               cdoSendUsingPort, value 2, for sending the message using the network.
                // smtpauthenticate:     Specifies the mechanism used when authenticating to an SMTP service over the network.
                //                                  Possible values are:
                //                                  - cdoAnonymous, value 0. Do not authenticate.
                //                                  - cdoBasic, value 1. Use basic clear-text authentication. (Hint: This requires the use of "sendusername" and "sendpassword" fields)
                //                                  - cdoNTLM, value 2. The current process security context is used to authenticate with the service.

                ADODB.Field field = fields["http://schemas.microsoft.com/cdo/configuration/smtpserver"];
                field.Value = settings.SMTPServerAddress;

                field = fields["http://schemas.microsoft.com/cdo/configuration/smtpserverport"];
                field.Value = settings.PortNumber;

                field = fields["http://schemas.microsoft.com/cdo/configuration/sendusing"];
                field.Value = CDO.CdoSendUsing.cdoSendUsingPort;

                field = fields["http://schemas.microsoft.com/cdo/configuration/smtpauthenticate"];
                field.Value = CDO.CdoProtocolsAuthentication.cdoBasic;

                field = fields["http://schemas.microsoft.com/cdo/configuration/sendusername"];
                field.Value = settings.Username;

                field = fields["http://schemas.microsoft.com/cdo/configuration/sendpassword"];
                field.Value = settings.Password;

                field = fields["http://schemas.microsoft.com/cdo/configuration/smtpusessl"];
                field.Value = "true";


                message.From = settings.SenderEmailAddress;
                message.To = settings.SenderEmailAddress;
                message.Subject = "Test";
                message.TextBody = settings.Content;

                // Send message.
                MessageBox.Show("Sent a message successfully");
            catch (Exception ex)
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