关于邮件的解码问题，RETR,POP3，邮件，附件,解码，邮件接收
大家好，我C＃.net（.NET Framework 2.0）中做一个邮件接收的程序。
利用里面的命名空间：
using System.Net;
using System.Net.Mail;
using System.Net.Mime;
using System.Net.Sockets;
using System.IO;
using System.Threading;
还使用了这些：
……
TcpClient tcpcnt= new TcpClient(txtPop3Server.Text, 110);
……
NetworkStream ns = null;
ns = tcpcnt.GetStream();
StreamReader sr = new StreamReader(ns);
……
现在遇到了问题，请大家来帮我看看。
我通过POP3中的RETR指令从我自己的邮箱（luyangfree@126.com）中接收里面
的邮件。
我的邮件里的内容是：
邮件的主题是：attachment
邮件的内容是：This is txt attachment.
邮件的附件是一个文本文件（ERR.txt），
文本文件里面的内容是：-ERR Unable to log on
以下是我邮件接收返回的信息：
+OK 2773 octets
Received: from mu-out-0910.google.com (unknown [209.85.134.191])
by mx15 (Coremail) with SMTP id wKjSpLDb7_LgJ+FFePnUEA==.40756S2;
Sun, 25 Feb 2007 14:08:33 +0800 (CST)
Received: by mu-out-0910.google.com with SMTP id g7so877445muf
for <luyangfree@126.com> ; Sat, 24 Feb 2007 22:08:29 -0800 (PST)
DKIM-Signature: a=rsa-sha1; c=relaxed/relaxed;
d=gmail.com; s=beta;
h=domainkey-signature:received:received:message-id:date:from:to:subject:mime-version:content-type;
b=R22Hv9U/n2fRhBbb/cMdNqp8eW80Q75Gir/xQON0UU1QpXi3iRLYX6ibHyItAQ/MQG4QBrfKj6PcbtcUTQ23TYRSHT8CacRXO0OY2uN+FkF51SMSdKWwVqSPtk+obZn+V4zjqFn1W3sU41pQ4kzLekPDhhRmJGJO6Z9sv8LXHvY=
DomainKey-Signature: a=rsa-sha1; c=nofws;
d=gmail.com; s=beta;
h=received:message-id:date:from:to:subject:mime-version:content-type;
b=kZEGW9fKxQLYjlL7VMI/WzpcZOY54q4IfVI7IWezg96dARAtpAj3fpl/NuySfuDhE3GOPxv7Tv79ClOKrKzwALURE4oJhoDEY/oyl7PeOldFYJzzk0oB3/ZXAJz6oOyvBfzXcUAN0F6q/AlFClV0cMLqB576uD0aV3/NaKDKmhI=
Received: by 10.82.135.13 with SMTP id i13mr1228808bud.1172383708921;
Sat, 24 Feb 2007 22:08:28 -0800 (PST)
Received: by 10.82.189.3 with HTTP; Sat, 24 Feb 2007 22:08:28 -0800 (PST)
Message-ID: <f9a9dfa70702242208j75854c3er4c40ab858c11414e@mail.gmail.com>
Date: Sun, 25 Feb 2007 14:08:28 +0800
From: "=?GB2312?B?wr3R7g==?= " <luyangfree@gmail.com>
To: luyangfree@126.com
Subject: attachment
MIME-Version: 1.0
Content-Type: multipart/mixed;
boundary= "----=_Part_49134_11090661.1172383708899 "
X-Coremail-Antispam: 1U3Yxn0WfASr-VFAUDIcSsGvfJT3xCjnVCjjxCrMxkI7II2jI
8vz4v_Cr0_Zr1lYx0Ex4A2jsIE14v26r4UJVWxJr1l6VACY4xI67k04243AwACY4xI67k0
4243AVC20s07MxkFs20EbsIEYx1lYx0E2Ix0cI8IcVAFwI0_Jrv_JF1lc2xSY4AK6IIF6r
47M7AC8VAFwI0_Jr0_Gr1l7I0Y6sxI4wAYFVCjjxCrM7CIcVAFz4kK6r1j6r18Mc02F40E
4c8EcI0Er2xKeI8DMc02F40EFcxC0VAKzVAqx4xG6I80ewAYjsxI4VWUJjkaLaAFLSUrUU
UUUjvjm3AaLaJ3UjIFyTuYvjxUUjg4DUUUUUAaLaJ3U
------=_Part_49134_11090661.1172383708899
Content-Type: multipart/alternative;
boundary= "----=_Part_49135_5869753.1172383708899 "
------=_Part_49135_5869753.1172383708899
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Content-Disposition: inline
This is txt attachment.
------=_Part_49135_5869753.1172383708899
Content-Type: text/html; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Content-Disposition: inline
This is txt attachment.
------=_Part_49135_5869753.1172383708899--
------=_Part_49134_11090661.1172383708899
Content-Type: text/plain; name= "ERR.txt "
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename= "ERR.txt "
X-Attachment-Id: f_eyl2zd46
LUVSUiBVbmFibGUgdG8gbG9nIG9u
------=_Part_49134_11090661.1172383708899--
请问，我应该怎么样做，才能实现接收回来的邮件内容的正常显示，
邮件附件的正确接收？
[解决办法]
这是 base64 编码，其中下面的行是分隔符
------=_Part_49135_5869753.1172383708899--
[解决办法]
------=_Part_49134_11090661.1172383708899
Content-Type: text/plain; name= "ERR.txt "
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename= "ERR.txt "
X-Attachment-Id: f_eyl2zd46
LUVSUiBVbmFibGUgdG8gbG9nIG9u
------=_Part_49134_11090661.1172383708899--
这是一个段。
必须找到这个段 段头信息和段体信息之间，有一个空行。
头信息说明，这是一个附件。内容是文本型，附件名为ERR.txt 传输编码是base6４
头信息必须解析，不然不能正确解析附件体
