邮件发送接收

string server = this.txtserver.Text;
                    MailMessage Mail = new MailMessage(this.txtFrom.Text, this.txtGet.Text);
                    Mail.Subject = this.txtSubject.Text.Trim().ToString();
                    Mail.Body = this.richTextBox1.Text.Trim().ToString();
                    SmtpClient Client = new SmtpClient("smtp.126.com",25);//实例一个SmtpClient类
                    //Client.UseDefaultCredentials = false;
                    Client.Credentials = new System.Net.NetworkCredential(txtusername.Text,txtpwd.Text);
                    Client.DeliveryMethod = SmtpDeliveryMethod.Network;
                    //Client.Host = "smtp.126.com";
                    //附件
                    if (txtAttach.Text.Length > 0)
                    {
                        Mail.Attachments.Add(new Attachment(txtAttach.Text, MediaTypeNames.Application.Octet));
                    }
                    Client.Send(Mail);

    TcpClient server;//接服务器
        string sendstring;//用于存储POP3服务命令参数
        byte[] bufferstring;//用于存储POP3服务命令参数字节数
        NetworkStream networkstream;//接服务器与服务器进行数据交互
        StreamReader streamreader;//读取信息数据
        private void btnConn_Click(object sender, EventArgs e)
        {
            //将光标置为等待状态
            Cursor cr = Cursor.Current;
            Cursor.Current = Cursors.WaitCursor;

            server = new TcpClient(this.txtPopserver.Text, 110);//实例TcpClient 类对象联接服务器
            networkstream = server.GetStream();//实例NetworkStream类对象接收返回发送的数据
            streamreader = new StreamReader(networkstream);//实例StreamReader类对象读取数据

            try
            {
                sendstring = "USER "+this.txtUserName.Text+"
";//存储用户名
                bufferstring = Encoding.GetEncoding("gb2312").GetBytes(sendstring.ToCharArray());
                networkstream.Write(bufferstring, 0, bufferstring.Length);//将用户名发送到服务器
                txtContent.AppendText(streamreader.ReadLine() + "
");//将用用户显示在 richTextBox控件中
                sendstring = "PASS " + this.txtPwd.Text + "
";//存储用户密码
                bufferstring = Encoding.GetEncoding("gb2312").GetBytes(sendstring.ToCharArray());
                networkstream.Write(bufferstring, 0, bufferstring.Length);//将用户密码发送到服务器
                txtContent.AppendText(streamreader.ReadLine() + "
");
                sendstring = "STAT " +"
";//储存从服务器获得所有信息序号和字节数命令
                bufferstring = Encoding.GetEncoding("gb2312").GetBytes(sendstring.ToCharArray());
                networkstream.Write(bufferstring, 0, bufferstring.Length);//从服务器获得所有信息序号和字节数
                string strResult=streamreader.ReadLine();//读取从服务器返回的数据
                if (strResult.IndexOf('-') == -1)
                {
                    txtContent.AppendText(strResult + "
");
                    sendstring = "LIST " + "
";//存储从服务器中获得信息列表和大小的命令
                    bufferstring = Encoding.GetEncoding("gb2312").GetBytes(sendstring.ToCharArray());
                    networkstream.Write(bufferstring, 0, bufferstring.Length);

                    string strInfo = streamreader.ReadLine();
                    string[] str = strInfo.Split(' ');

                    txtContent.AppendText("邮件数量：" + str[1] + "
");
                    txtContent.AppendText(str[1] + ":封邮件总容量为" + str[2] + "
");

                    MessageBox.Show(this.txtUserName.Text + "用户您好！！！");
                     btnAccept.Enabled = true;
                    //将光标置回原来的状态
                    Cursor.Current = cr;
                    btnDisconn.Enabled = true;
                    btnConn.Enabled = false;
                }
                else
                {
                    MessageBox.Show("读取信息有误，请重新登录");
                }
            }
            catch (Exception ey)
            {
                MessageBox.Show(ey.Message);
            }
        }
        private void Showinfo()
        {
            Cursor cr = Cursor.Current;//定义鼠标信息
            Cursor.Current = Cursors.WaitCursor;
            this.txtContent.Clear();
            try
            {
                string strResult = "";
                sendstring = "RETR " + this.txtEmailIndex.Text + "
";//存储从服务器获得一条信息的命令
                bufferstring = Encoding.ASCII.GetBytes(sendstring.ToCharArray());
                networkstream.Write(bufferstring, 0, bufferstring.Length);
                strResult = streamreader.ReadLine();
                if (strResult[0] != '-')
                {
                    //不断地读取邮件内容，只到结束标志：英文句号
                    while (strResult != ".")
                    {
                        this.txtContent.AppendText(strResult + "
");
                        strResult = streamreader.ReadLine();
                    }
                }
                else
                {
                    this.txtContent.AppendText("
" + "邮件错误" + "
");
                }
            }
            catch (Exception ey)
            {
                MessageBox.Show(ey.Message);
            }
            Cursor.Current = cr;
        }

        private void btnDisconn_Click(object sender, EventArgs e)
        {
            //将光标置为等待状态
            Cursor cr = Cursor.Current;
            Cursor.Current = Cursors.WaitCursor;
            txtContent.Clear();
            
            //向服务器发送QUIT命令从而结束和POP3服务器的会话
            sendstring ="QUIT"+this.txtUserName.Text+"
";
            bufferstring = Encoding.ASCII.GetBytes(sendstring.ToCharArray());
            networkstream.Write(bufferstring, 0, bufferstring.Length);
            txtContent.AppendText(streamreader.ReadLine() + "
");

            //断开连接
            networkstream.Close();
            streamreader.Close();

            //改变按钮的状态
            btnConn.Enabled = true;
            btnDisconn.Enabled = false;
            btnAccept.Enabled = false;

            //将光标置回原来的状态
            Cursor.Current = cr; 
        }