[求助] 求教高手，用程序调用失败，为何？

求教高手，emos1.5，普通发信无误，用程序调用smtp失败。程序如下。为何？

private bool SendEmail()
      {
         //连接网络
         try
         {
            tc = new TcpClient(mailserver, mailserverport);
         }
         catch (Exception e)
         {
            Trip8.Common.ILog.LogWrite(Trip8.Common.Configuration.LogEmail, "SendEmail()" + e.Message);

            errmsg = e.ToString();
            return false;
         }

         ns = tc.GetStream();
         SMTPCodeAdd();

         //验证网络连接是否正确
         if (RightCodeHT[RecvResponse().Substring(0, 3)] == null)
         {
            Trip8.Common.ILog.LogWrite(Trip8.Common.Configuration.LogEmail, "SendEmail()+网络连接失败");

            errmsg = "网络连接失败";
            return false;
         }

         string[] SendBuffer;
         string SendBufferstr;

         //进行SMTP验证
         if (ESmtp)
         {
            SendBuffer = new String[4];
            SendBuffer[0] = "EHLO " + mailserver + enter;
            SendBuffer[1] = "AUTH LOGIN" + enter;
            SendBuffer[2] = Base64Encode(username) + enter;
            SendBuffer[3] = Base64Encode(password) + enter;
            if (!Dialog(SendBuffer, "SMTP服务器验证失败，请核对用户名和密码。"))
            {
                  Trip8.Common.ILog.LogWrite(Trip8.Common.Configuration.LogEmail, "SendEmail()+SMTP服务器验证失败，请核对用户名和密码。");

                  return false;
            }
         }
         else
         {
            SendBufferstr = "HELO " + mailserver + enter;
            if (!Dialog(SendBufferstr, ""))
                  return false;
         }

         //
         SendBufferstr = "MAIL FROM:<" + From + ">" + enter;
         if (!Dialog(SendBufferstr, "发件人地址错误，或不能为空"))
         {
            Trip8.Common.ILog.LogWrite(Trip8.Common.Configuration.LogEmail, "SendEmail()+发件人地址错误，或不能为空。");

            return false;
         }

         //
         SendBuffer = new string[recipientmaxnum];
         for (int i = 0; i < Recipient.Count; i++)
         {
            SendBuffer = "RCPT TO:<" + Recipient.ToString() + ">" + enter;

         }
         if (!Dialog(SendBuffer, "收件人地址有误"))
         {
            Trip8.Common.ILog.LogWrite(Trip8.Common.Configuration.LogEmail, "SendEmail()+收件人地址有误。");

            return false;
         }

         /*
                     SendBuffer=new string[10];
                     for(int i=0;i<RecipientBCC.Count;i++)
                     {

                        SendBuffer="RCPT TO:<" + RecipientBCC.ToString() +">" + enter;

                     }

                     if(!Dialog(SendBuffer,"密件收件人地址有误"))
                        return false;
         */
         SendBufferstr = "DATA" + enter;
         if (!Dialog(SendBufferstr, ""))
            return false;

         SendBufferstr = "From:" + FromName + "<" + From + ">" + enter;

         //if(ReplyTo.Trim()!="")
         //{
         // SendBufferstr+="Reply-To: " + ReplyTo + enter;
         //}

         //SendBufferstr+="To:" + RecipientName + "<" + Recipient[0] +">" +enter;
         SendBufferstr += "To:=?" + Charset.ToUpper() + "?B?" + Base64Encode(RecipientName) + "?=" + "<" + Recipient[0] + ">" + enter;

         SendBufferstr += "CC:";
         for (int i = 1; i < Recipient.Count; i++)
         {
            SendBufferstr += Recipient.ToString() + "<" + Recipient.ToString() + ">,";
         }
         SendBufferstr += enter;

         SendBufferstr += ((Subject == String.Empty || Subject == null) ? "Subject:" : ((Charset == "") ? ("Subject:" + Subject) : ("Subject:" + "=?" + Charset.ToUpper() + "?B?" + Base64Encode(Subject) + "?="))) + enter;
         SendBufferstr += "X-Priority:" + priority.ToString() + enter;
         SendBufferstr += "X-MSMail-Priority:" + priority.ToString() + enter;
         SendBufferstr += "Importance:" + priority.ToString() + enter;
         SendBufferstr += "X-Mailer: ProgramProbe.CommunicationProxy.SmtpMailHelper [cn]" + enter;
         SendBufferstr += "MIME-Version: 1.0" + enter;
         if (Attachments.Count != 0)
         {
            SendBufferstr += "Content-Type: multipart/mixed;" + enter;
            SendBufferstr += " boundary=\"=====" + (Html ? "001_Dragon520636771063_" : "001_Dragon303406132050_") + "=====\"" + enter + enter;
         }

         if (Html)
         {
            if (Attachments.Count == 0)
            {
                  SendBufferstr += "Content-Type: multipart/alternative;" + enter;//内容格式和分隔符
                  SendBufferstr += " boundary=\"=====003_Dragon520636771063_=====\"" + enter + enter;

                  SendBufferstr += "This is a multi-part message in MIME format." + enter + enter;
            }
            else
            {
                  SendBufferstr += "This is a multi-part message in MIME format." + enter + enter;
                  SendBufferstr += "--=====001_Dragon520636771063_=====" + enter;
                  SendBufferstr += "Content-Type: multipart/alternative;" + enter;//内容格式和分隔符
                  SendBufferstr += " boundary=\"=====003_Dragon520636771063_=====\"" + enter + enter;
            }
            SendBufferstr += "--=====003_Dragon520636771063_=====" + enter;
            SendBufferstr += "Content-Type: text/plain;" + enter;
            SendBufferstr += ((Charset == "") ? (" charset=\"iso-8859-1\"") : (" charset=\"" + Charset.ToLower() + "\"")) + enter;
            SendBufferstr += "Content-Transfer-Encoding: base64" + enter + enter;
            SendBufferstr += Base64Encode("邮件内容为HTML格式，请选择HTML方式查看") + enter + enter;

            SendBufferstr += "--=====003_Dragon520636771063_=====" + enter;

            SendBufferstr += "Content-Type: text/html;" + enter;
            SendBufferstr += ((Charset == "") ? (" charset=\"iso-8859-1\"") : (" charset=\"" + Charset.ToLower() + "\"")) + enter;
            SendBufferstr += "Content-Transfer-Encoding: base64" + enter + enter;
            SendBufferstr += Base64Encode(Body) + enter + enter;
            SendBufferstr += "--=====003_Dragon520636771063_=====--" + enter;
         }
         else
         {
            if (Attachments.Count != 0)
            {
                  SendBufferstr += "--=====001_Dragon303406132050_=====" + enter;
            }
            SendBufferstr += "Content-Type: text/plain;" + enter;
            SendBufferstr += ((Charset == "") ? (" charset=\"iso-8859-1\"") : (" charset=\"" + Charset.ToLower() + "\"")) + enter;
            SendBufferstr += "Content-Transfer-Encoding: base64" + enter + enter;
            SendBufferstr += Base64Encode(Body) + enter;
         }

         //SendBufferstr += "Content-Transfer-Encoding: base64"+enter;

         if (Attachments.Count != 0)
         {
            for (int i = 0; i < Attachments.Count; i++)
            {
                  string filepath = (string)Attachments;
                  SendBufferstr += "--=====" + (Html ? "001_Dragon520636771063_" : "001_Dragon303406132050_") + "=====" + enter;
                  //SendBufferstr += "Content-Type: application/octet-stream"+enter;
                  SendBufferstr += "Content-Type: text/plain;" + enter;
                  SendBufferstr += " name=\"=?" + Charset.ToUpper() + "?B?" + Base64Encode(filepath.Substring(filepath.LastIndexOf("\\") + 1)) + "?=\"" + enter;
                  SendBufferstr += "Content-Transfer-Encoding: base64" + enter;
                  SendBufferstr += "Content-Disposition: attachment;" + enter;
                  SendBufferstr += " filename=\"=?" + Charset.ToUpper() + "?B?" + Base64Encode(filepath.Substring(filepath.LastIndexOf("\\") + 1)) + "?=\"" + enter + enter;
                  SendBufferstr += GetStream(filepath) + enter + enter;
            }
            SendBufferstr += "--=====" + (Html ? "001_Dragon520636771063_" : "001_Dragon303406132050_") + "=====--" + enter + enter;
         }

         SendBufferstr += enter + "." + enter;

         if (!Dialog(SendBufferstr, "错误信件信息"))
            return false;

         SendBufferstr = "QUIT" + enter;
         if (!Dialog(SendBufferstr, "断开连接时错误"))
            return false;

         ns.Close();
         tc.Close();
         return true;
      }