总结:.用asp.net 2.0发送邮件非常的方便,只需要用using System.Net.Mail命名空间下的类就可以完成发送邮件的功能,发送邮件的服务器可以有以下几种情况:
1.本地的smtp服务器
2.网络上的smtp服务器(smtp.163.com等)
以下是我测试发送邮件的范例,基本上都考虑到的所有的情况,如果还有什么没有考虑到的请给我留言,我接续完善其功能.
1.新建一网站名字叫SentEmailText.
2.添加一个新的页面default.aspx
代码如下:

<form id="Form1" runat="server" method="post">
     <div id="content">
                 <div id="msg">
                    <div id="msg_title">Send Email Test</div>
                    <div id="msg_prompt"></div>
                    <asp:ValidationSummary id="msg_alarm" runat="server"></asp:ValidationSummary>
                </div>
                <div id="form">
                     <div>
                        <label for="SmtpServerText">Sever name:</label>
                        <input type="text"  id="SmtpServerText" name="SmtpServerText" runat="server" />
                    </div>
                     <div>
                        <label for="SmtpServerPort">Sever Port:</label>
                        <input type="text" id="SmtpServerPort"  name="SmtpServerPort" runat="server" />
                    </div>
                     <div>
                        <label for="UserName">User Name:</label>
                        <input type="text"  name="UserName" id="UserName" runat="server" />
                    </div>
                     <div>
                        <label for="Pwd">Pwd:</label>
                        <input type="text"  name="Pwd" runat="server" id="Pwd" />
                    </div>
                     <div>
                        <label for="FromAddress">From Address:</label>
                        <input type="text"  name="FromAddress" runat="server" id="FromAddress" />
                    </div>
                     <div>
                        <label for="SendAddress">Send Address:</label>
                        <input type="text"  name="SendAddress" runat="server" id="SendAddress" />
                    </div>
                     <div>
                        <label for="attachment">Attachment:</label>
                        <input type="file" runat="server" name="attachment" id="attachment" />
                    </div>
                     <div>
                        <label for="txtSubject">Email Subject:</label>
                        <input type="text"  name="txtSubject" runat="server" id="txtSubject" />
                    </div>
                    <div>
                        <label for="txtBody">Email Body:</label>
                        <textarea name="txtBody" runat="server" rows="10" cols="50" id="txtBody"></textarea>
                    </div>
                    <div>
                        &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
                        <input type="submit" value="Send Email" class="prim" id="btnSend" runat="server" onserverclick="btnSend_ServerClick" />
                    </div>
                </div>
       </div>
    </form>

3.新建一个style的文件夹,添加样式页面,主要功能是表单的对齐样式,比较通用的设置(见附件)
4.添加一个mail的类文件,注意用于发送邮件考虑的几种情况(见附件)

using System;
using System.Text; 
using System.Net.Mail;
using System.Net.Sockets;
using System.IO;
public class Mail
{
  "Custom var"

  "Property"

  "OverLoad"

  "Send Emial including groups and attachment"

  /// <summary>
  /// Received Email
  /// </summary>
    public void ReseiveMail()
    {
        string ServerHost = "pop3."+this._Host ;
        TcpClient tcp = new TcpClient(ServerHost, 110);
        NetworkStream ns = tcp.GetStream();
        StreamReader sr = new StreamReader(ns);
        StreamWriter sw = new StreamWriter(ns);
     }
 }

5.页面调用方式参见附件
6.附件下载附件(源代码下载)