我在C#中接收Email的问题

using System.Net.Sockets; 
using System.IO; 
using System.Net; 
using System;class POP 
{ 
string POPServer; 
string user; 
string pwd; 
public POP(){} 
public POP(string server, string _user, string _pwd) 
{ 
POPServer = server; 
user = _user; 
pwd = _pwd; 
} 
private NetworkStream Connect() 
{ 
TCPClient sender = new TCPClient(POPServer,110); 
Byte[] outbytes; 
string input; 
NetworkStream ns = null; 
try{ 
ns = sender.GetStream(); 
StreamReader sr = new StreamReader(ns); 
Console.WriteLine(sr.ReadLine() );input = "user " + user + "\r\n"; 
outbytes = System.Text.Encoding.ASCII.GetBytes
(input.ToCharArray()); 
ns.Write(outbytes,0,outbytes.Length) ; 
Console.WriteLine(sr.ReadLine() );input = "pass " + pwd + "\r\n"; 
outbytes = System.Text.Encoding.ASCII.GetBytes
(input.ToCharArray()); 
ns.Write(outbytes,0,outbytes.Length) ; 
Console.WriteLine(sr.ReadLine() );return ns; 
} 
catch(InvalidOperationException ioe){ 
Console.WriteLine("Could not connect to mail server"); 
return ns; 
} 
} 
public int GetNumberOfNewMessages() 
{ 
Byte[] outbytes; 
string input; 
try{ 
NetworkStream ns = Connect(); 
StreamReader sr = new StreamReader(ns);input = "stat" + "\r\n"; 
outbytes = System.Text.Encoding.ASCII.GetBytes
(input.ToCharArray()); 
ns.Write(outbytes,0,outbytes.Length); 
string resp = sr.ReadLine(); 
Console.WriteLine(resp); 
string[] tokens = resp.Split(new Char[] {' '});input = "quit" + "\r\n"; 
outbytes = System.Text.Encoding.ASCII.GetBytes
(input.ToCharArray()); 
ns.Write(outbytes,0,outbytes.Length); 
Console.WriteLine(sr.ReadLine());sr.Close(); 
ns.Close(); 
return tokens[1].ToInt32(); 
} 
catch(InvalidOperationException ioe){ 
Console.WriteLine("Could not connect to mail server"); 
return 0; 
} 
} 
public static void Main() 
{ 
POP pop = new POP("pop-server", "loginname", "password"); 
Console.WriteLine("New Messages = {0}", 
pop.GetNumberOfNewMessages() ); 
Console.ReadLine(); 
} 
}   
======================
命令解析部分private bool SwitchCommand(string POP3_commandTxt)
{
try
{
//---- Parse command --------------------------------------------------//
string[] cmdParts = POP3_commandTxt.TrimStart().Split(new char[]{' '});
string POP3_command = cmdParts[0];
   POP3_command = POP3_command.ToUpper();
//---------------------------------------------------------------------// //----- loging stuff --------------------------------------------------------------------------//
if(m_pPOP3_Server.LogCommands){
string lCmdTxt = POP3_commandTxt.Replace("\r\n","<CRLF>");
m_pLogWriter.AddEntry(lCmdTxt,this.SessionID,m_ConnectedIp,"C");
}
//---- End of loging ---------------------------------------------------------------------------// switch(POP3_command)
{
case "USER":
USER(Core.GetArgsText(POP3_commandTxt,"USER"));
break; case "PASS":
PASS(Core.GetArgsText(POP3_commandTxt,"PASS"));
break;

case "STAT":
STAT();
break; case "LIST":
LIST(Core.GetArgsText(POP3_commandTxt,"LIST"));
break; case "RETR":
RETR(Core.GetArgsText(POP3_commandTxt,"RETR"));
break; case "DELE":
DELE(Core.GetArgsText(POP3_commandTxt,"DELE"));
break; case "NOOP":
NOOP();
break; case "RSET":
RSET();
break; case "QUIT":
QUIT();
return true;
//----- Optional commands ----- //
case "UIDL":
UIDL(Core.GetArgsText(POP3_commandTxt,"UIDL"));
break; case "APOP":
APOP(Core.GetArgsText(POP3_commandTxt,"APOP"));
break; case "TOP":
TOP(Core.GetArgsText(POP3_commandTxt,"TOP"));
break;

default:
SendData("-ERR Invalid command\r\n"); //---- Check that maximum bad commands count isn't exceeded ---------------//
if(m_BadCmdCount > m_pPOP3_Server.MaxBadCommands-1){
SendData("421 Too many bad commands, closing transmission channel\r\n");
return true;
}
m_BadCmdCount++;
//-------------------------------------------------------------------------// break;

}
}
catch(Exception x)
{
// Connection lost
if(!m_pClientSocket.Connected){
return true;
}

SendData("-ERR Unkown temp error\r\n");
m_pPOP3_Server.OnSysError(x,new System.Diagnostics.StackTrace());
}

return false;
}===========================
我做了一个pop3接收客户端，在收取邮件时，服务器返回得内容如下：+OK Return-Path: <[email protected]>Delivered-To: [email protected]: (qmail 32409 invoked from network); 28 Nov 2002 01:31:31 -0000Received: from unknown (HELO 21cn.com) (61.140.60.248)  by 202.106.187.186 with SMTP; 28 Nov 2002 01:31:31 -0000Received: from 21cn.com([127.0.0.1]) by 21cn.com(AIMC 2.9.5.6) with SMTP id jm93de57653; Thr, 28 Nov 2002 09:48:55 +0800Received: from 21cn.com([10.2.2.1]) by 21cn.com(AIMC 2.9.5.1) with SMTP id jm73de5e038; Thr, 28 Nov 2002 09:48:55 +0800Content-Type: text/plainContent-Transfer-Encoding: 8bitMIME-Version: 1.0Message-ID: <[email protected]>X-AIMailer: AIMC 2.9.5.6 2002.10.10X-AIMime: MIME/SMIME Lib 2.9 2.9 2002.10.10Date: Thu, 28 Nov 2002 09:34:33 +0800 (CST)From: "??????"<[email protected]>To: yysscheng <[email protected]>Cc: Subject: =?gb2312?b?sOy5q9fUtq+7rw==?=X-Priority: 3X-Originating-IP: 61.163.14.2X-AIMC-AUTH: (null)X-AIMC-MAILFROM: [email protected]??????    ??????????????????????????    ??????????                          ??????             11.28----------------------------------------------?????????????????????????????????? http://y.21cn.com ????A??210099???????????????????? http://sms.21cn.com/baobei/sjsy.html 21CN??????3??????12??10?????????? http://mail.21cn.com/huodong/9yue/ 21CN????????????????????????U?? http://mail.21cn.com/huodong/11yue/business/ 其中的汉字如何解析出来？
（注：我得连接类如下：
public class Pop3Connection
{
private TcpClient socket;
private StreamReader reader;
private StreamWriter writer;
private bool connected;
public bool Connected
{
get{return connected;}
}
public Pop3Connection()
{
// TODO: 在此处添加构造函数逻辑
connected=false;
socket=new TcpClient();
}
~Pop3Connection()
{
socket=null;
}
internal void Open(string host,int port)
{
if(host==null || host.Trim()=="")
{
throw new ArgumentException("Host is null!");
}
if(port<0)
{
throw new ArgumentException("Port is invalid!");
}
try
{ socket.Connect(host,port);
reader=new StreamReader(socket.GetStream(),System.Text.Encoding.ASCII );
writer=new StreamWriter(socket.GetStream(),System.Text.Encoding.ASCII);
connected=true;
}
catch(Exception e)
{
connected=false;
}
}
internal void SendCommand(string cmd)
{
writer.WriteLine(cmd);
writer.Flush();
}
internal void GetReply(out string reply )
{
if(Connected)
{reply=reader.ReadLine();}
else
{reply="";}
}
internal void Close()
{
reader.Close();
writer.Flush();
writer.Close();
reader=null;
writer=null;
socket.Close();
connected=false;
}
}
）