发邮件界面：

收邮件界面：

先分析邮件发送类

邮件发送类使用smtp协议，这里以QQ邮箱为例

using System;using System.Collections.Generic;using System.ComponentModel;using System.Data;using System.Drawing;using System.Text;using System.Windows.Forms;//添加的命名空间引用using System.Net;using System.Net.Mail;using System.IO;using System.Net.Mime;namespace SendMailExample{    public partial class FormSendMail : Form    {        public FormSendMail()        {            InitializeComponent();        }        private void FormSendMail_Load(object sender, EventArgs e)        {            //邮箱协议            textBoxSmtpServer.Text = "smtp.qq.com";            //发送人邮箱            textBoxSend.Text = "邮箱账号";            //发送人姓名            textBoxDisplayName.Text = "名字";            //密码            textBoxPassword.Text = "邮箱密码";            //收件人姓名            textBoxReceive.Text = "收件人邮箱账号";            //发送标题            textBoxSubject.Text = "测试mytest";            //发送内容            textBoxBody.Text = "This is a test（测试）";            radioButtonSsl.Checked = true;        }        //单击【发送】按钮触发的事件        private void buttonSend_Click(object sender, EventArgs e)        {            this.Cursor = Cursors.WaitCursor;            //实例化一个发送邮件类            MailMessage mailMessage = new MailMessage();            //发件人邮箱，方法重载不同，可以根据需求自行选择            mailMessage.From = new MailAddress(textBoxSend.Text, textBoxDisplayName.Text, System.Text.Encoding.UTF8);            //收件人邮箱地址            mailMessage.To.Add(textBoxReceive.Text);            //邮件标题            mailMessage.Subject = textBoxSubject.Text;            //邮件发送使用的编码            mailMessage.SubjectEncoding = System.Text.Encoding.Default;            //邮件发送的内容            mailMessage.Body = textBoxBody.Text;            //发送邮件的标题            mailMessage.BodyEncoding = System.Text.Encoding.Default;            //指定邮件是否为html格式            mailMessage.IsBodyHtml = false;            //设置电子邮件的优先级            mailMessage.Priority = MailPriority.Normal;            //添加附件            Attachment attachment = null;            if (listBoxFileName.Items.Count > 0)            {                for (int i = 0; i < listBoxFileName.Items.Count; i++)                {                    string pathFileName = listBoxFileName.Items[i].ToString();                    string extName = Path.GetExtension(pathFileName).ToLower();                    //这里仅举例说明如何判断附件类型                    if (extName == ".rar" || extName == ".zip")                    {                        attachment = new Attachment(pathFileName, MediaTypeNames.Application.Zip);                    }                    else                    {                        attachment = new Attachment(pathFileName, MediaTypeNames.Application.Octet);                    }                    ContentDisposition cd = attachment.ContentDisposition;                    cd.CreationDate = File.GetCreationTime(pathFileName);                    cd.ModificationDate = File.GetLastWriteTime(pathFileName);                    cd.ReadDate = File.GetLastAccessTime(pathFileName);                    mailMessage.Attachments.Add(attachment);                }            }            SmtpClient smtpClient = new SmtpClient();            smtpClient.Host = textBoxSmtpServer.Text;            smtpClient.Port = 25;            //是否使用安全套接字层加密连接            smtpClient.EnableSsl = radioButtonSsl.Checked;            //不使用默认凭证,注意此句必须放在client.Credentials的上面            smtpClient.UseDefaultCredentials = false;            smtpClient.Credentials = new NetworkCredential(textBoxSend.Text, textBoxPassword.Text);            //邮件通过网络直接发送到服务器            smtpClient.DeliveryMethod = SmtpDeliveryMethod.Network;            try            {                smtpClient.Send(mailMessage);                MessageBox.Show("发送成功");            }            catch (SmtpException smtpError)            {                MessageBox.Show("发送失败:" + smtpError.StatusCode                    + "\n\n" + smtpError.Message                    + "\n\n" + smtpError.StackTrace);            }            finally            {                mailMessage.Dispose();                smtpClient = null;                this.Cursor = Cursors.Default;            }        }        //单击【添加附件】按钮触发的事件        private void buttonAddAttachment_Click(object sender, EventArgs e)        {            //提示用户打开一个文件夹            OpenFileDialog myOpenFileDialog = new OpenFileDialog();            myOpenFileDialog.CheckFileExists = true;            //只接收有效的文件名            myOpenFileDialog.ValidateNames = true;            //允许一次选择多个文件作为附件            myOpenFileDialog.Multiselect = true;            myOpenFileDialog.ShowDialog();            if (myOpenFileDialog.FileNames.Length > 0)            {                listBoxFileName.Items.AddRange(myOpenFileDialog.FileNames);            }        }    }}

 

 收邮件的代码:

using System;using System.Collections.Generic;using System.ComponentModel;using System.Data;using System.Drawing;using System.Text;using System.Windows.Forms;//添加的命名空间引用using System.Net;using System.Net.Sockets;using System.IO;namespace ReceiveMailExample{    public partial class FormReceiveMail : Form    {        private TcpClient tcpClient;        private NetworkStream networkStream;        private StreamReader sr;        private StreamWriter sw;        public FormReceiveMail()        {            InitializeComponent();            textBoxPOP3Server.Text = "pop.qq.com";            textBoxPassword.Text = "密码";            textBoxUser.Text = "邮箱账号";        }        //单击建立连接按钮触发的事件        private void buttonConnect_Click(object sender, EventArgs e)        {            Cursor.Current = Cursors.WaitCursor;            listBoxStatus.Items.Clear();            try            {                //建立与POP3服务器的连接，使用默认端口110                tcpClient = new TcpClient(textBoxPOP3Server.Text,110);                listBoxStatus.Items.Add("与pop3服务器连接成功");            }            catch            {                MessageBox.Show("与服务器连接失败");                return;            }            string str;            networkStream = tcpClient.GetStream();            //得到输入流            sr = new StreamReader(networkStream, Encoding.Default);            //得到输出流            sw = new StreamWriter(networkStream, Encoding.Default);            sw.AutoFlush = true;            //读取服务器回送的连接信息            str = GetResponse();            if (CheckResponse(str) == false) return;            //向服务器发送用户名，请求确认            SendToServer("USER " + textBoxUser.Text);            str = GetResponse();            if (CheckResponse(str) == false) return;            //向服务器发送密码，请求确认            SendToServer("PASS " + textBoxPassword.Text);            str = GetResponse();            if (CheckResponse(str) == false) return;            //向服务器发送LIST命令，请求获取邮件总数和总字节数            SendToServer("LIST");            str = GetResponse();            if (CheckResponse(str) == false) return;            string[] splitString = str.Split(' ');            //从字符串中取子串获取邮件总数            int count = int.Parse(splitString[1]);            //判断邮箱中是否有邮件            if (count > 0)            {                listBoxOperation.Items.Clear();                groupBoxOperation.Text = "信箱中共有 " + splitString[1] + " 封邮件";                //向邮件列表框中添加邮件                for (int i = 0; i < count; i++)                {                    str = GetResponse();                    splitString = str.Split(' ');                    listBoxOperation.Items.Add(string.Format(                        "第{0}封：{1}字节", splitString[0], splitString[1]));                }                listBoxOperation.SelectedIndex = 0;                //读出结束符                str = GetResponse();                //设置对应状态信息                buttonRead.Enabled = true;                buttonDelete.Enabled = true;            }            else            {                groupBoxOperation.Text = "信箱中没有邮件";                buttonRead.Enabled = false;                buttonDelete.Enabled = false;            }            buttonConnect.Enabled = false;            buttonDisconnect.Enabled = true;            Cursor.Current = Cursors.Default;        }        private bool SendToServer(string str)        {            try            {                sw.WriteLine(str);                sw.Flush();                listBoxStatus.Items.Add("发送：" + str);                return true;            }            catch (Exception err)            {                listBoxStatus.Items.Add("发送失败：" + err.Message);                return false;            }        }        private string GetResponse()        {            string str = null;            try            {                str = sr.ReadLine();                if (str == null)                {                    listBoxStatus.Items.Add("收到：null");                }                else                {                    listBoxStatus.Items.Add("收到：" + str);                    if (str.StartsWith("-ERR"))                    {                        str = null;                    }                }            }            catch (Exception ex)            {                listBoxStatus.Items.Add("接收失败：" + ex.Message);            }            return str;        }        private bool CheckResponse(string responseString)        {            if (responseString == null)            {                return false;            }            else            {                if (responseString.StartsWith("+OK"))                {                    return true;                }                else                {                    return false;                }            }        }        //单击断开连接按钮触发的事件        private void buttonDisconnect_Click(object sender, EventArgs e)        {            SendToServer("QUIT");            sr.Close();            sw.Close();            networkStream.Close();            tcpClient.Close();            listBoxOperation.Items.Clear();            richTextBoxOriginalMail.Clear();            listBoxStatus.Items.Clear();            groupBoxOperation.Text = "邮件信息";            buttonConnect.Enabled = true;            buttonDisconnect.Enabled = false;        }        //单击阅读信件按钮触发的事件        private void buttonRead_Click(object sender, EventArgs e)        {            Cursor.Current = Cursors.WaitCursor;            richTextBoxOriginalMail.Clear();            string mailIndex = listBoxOperation.SelectedItem.ToString();            mailIndex = mailIndex.Substring(1, mailIndex.IndexOf("封") - 1);            SendToServer("RETR " + mailIndex);            string str = GetResponse();            if (CheckResponse(str) == false) return;            try            {                string receiveData = sr.ReadLine();                if (receiveData.StartsWith("-ERR") == true)                {                    listBoxStatus.Items.Add(receiveData);                }                else                {                    while (receiveData != ".")                    {                        richTextBoxOriginalMail.AppendText(receiveData + "\r\n");                        receiveData = sr.ReadLine();                    }                }            }            catch (InvalidOperationException err)            {                listBoxStatus.Items.Add("Error: " + err.ToString());            }            Cursor.Current = Cursors.Default;        }        private void DecodeMailHeader(string mail)        {            string header = "";            int pos = mail.IndexOf("\n\n");            if (pos == -1)            {                header = GetDecodedHeader(mail);            }            else            {                header = mail.Substring(0, pos + 2);            }            //richTextBoxDecode.AppendText(GetDecodedHeader(header));        }        private string GetDecodedHeader(string header)        {            StringBuilder s = new StringBuilder();            s.AppendLine("Subject:" + GetEncodedValueString(header, "Subject: ", false));            s.AppendLine("From:" + GetEncodedValueString(header, "From: ", false).Trim());            s.AppendLine("To:" + GetEncodedValueString(header, "To: ", true).Trim());            s.AppendLine("Date:" + GetDateTimeFromString(GetValueString(header, "Date: ", false, false)));            s.AppendLine("Cc:" + GetEncodedValueString(header, "Cc: ", true).Trim());            s.AppendLine("ContentType:" + GetValueString(header, "Content-Type: ", false, true));            return s.ToString();        }        /// 
        /// 把时间转成字符串形式        /// 
        ///         /// 
             private string GetDateTimeFromString(string DateTimeString)        {            if (DateTimeString == "")            {                return null;            }            try            {                string strDateTime;                if (DateTimeString.IndexOf("+") != -1)                {                    strDateTime = DateTimeString.Substring(0, DateTimeString.IndexOf("+"));                }                else if (DateTimeString.IndexOf("-") != -1)                {                    strDateTime = DateTimeString.Substring(0, DateTimeString.IndexOf("-"));                }                else                {                    strDateTime = DateTimeString;                }                DateTime dt = DateTime.Parse(strDateTime);                return dt.ToString();            }            catch            {                return null;            }        }        private string GetEncodedValueString(string SourceString, string Key, bool SplitBySemicolon)        {            int j;            string strValue;            string strSource = SourceString.ToLower();            string strReturn = "";            j = strSource.IndexOf(Key.ToLower());            if (j != -1)            {                j += Key.Length;                int kk = strSource.IndexOf("\n", j);                strValue = SourceString.Substring(j, kk - j).TrimEnd();                do                {                    if (strValue.IndexOf("=?") != -1)                    {                        if (SplitBySemicolon == true)                        {                            strReturn += ConvertStringEncodingFromBase64(strValue) + "; ";                        }                        else                        {                            strReturn += ConvertStringEncodingFromBase64(strValue);                        }                    }                    else                    {                        strReturn += strValue;                    }                    j += strValue.Length + 2;                    if (strSource.IndexOf("\r\n", j) == -1)                    {                        break;                    }                    else                    {                        strValue = SourceString.Substring(j, strSource.IndexOf("\r\n", j) - j).TrimEnd();                    }                }                while (strValue.StartsWith(" ") || strValue.StartsWith("\t"));            }            else            {                strReturn = "";            }            return strReturn;        }        private string GetValueString(string SourceString, string Key, bool ContainsQuotationMarks, bool ContainsSemicolon)        {            int j;            string strReturn;            string strSource = SourceString.ToLower();            j = strSource.IndexOf(Key.ToLower());            if (j != -1)            {                j += Key.Length;                strReturn = SourceString.Substring(j, strSource.IndexOf("\n", j) - j).TrimStart().TrimEnd();                if (ContainsSemicolon == true)                {                    if (strReturn.IndexOf(";") != -1)                    {                        strReturn = strReturn.Substring(0, strReturn.IndexOf(";"));                    }                }                if (ContainsQuotationMarks == true)                {                    int i = strReturn.IndexOf("\"");                    int k;                    if (i != -1)                    {                        k = strReturn.IndexOf("\"", i + 1);                        if (k != -1)                        {                            strReturn = strReturn.Substring(i + 1, k - i - 1);                        }                        else                        {                            strReturn = strReturn.Substring(i + 1);                        }                    }                }                return strReturn;            }            else            {                return "";            }        }        private string ConvertStringEncodingFromBase64(string SourceString)        {            try            {                if (SourceString.IndexOf("=?") == -1)                {                    return SourceString;                }                else                {                    int i = SourceString.IndexOf("?");                    int j = SourceString.IndexOf("?", i + 1);                    int k = SourceString.IndexOf("?", j + 1);                    char chrTransEnc = SourceString[j + 1];                    switch (chrTransEnc)                    {                        case 'B':                            return ConvertStringEncodingFromBase64Ex(SourceString.Substring(k + 1, SourceString.IndexOf("?", k + 1) - k - 1), SourceString.Substring(i + 1, j - i - 1));                        default:                            throw new Exception("unhandled content transfer encoding");                    }                }            }            catch            {                return "";            }        }        /// 
        /// 把Base64编码转换成字符串        /// 
        ///         ///         /// 
             private string ConvertStringEncodingFromBase64Ex(string SourceString, string Charset)        {            try            {                Encoding enc;                if (Charset == "")                    enc = Encoding.Default;                else                    enc = Encoding.GetEncoding(Charset);                return enc.GetString(Convert.FromBase64String(SourceString));            }            catch            {                return "";            }        }        /// 
        /// 把字符串转换成Base64Ex编码        /// 
        ///         ///         ///         /// 
             private string ConvertStringEncodingToBase64Ex(string SourceString, string Charset, bool AutoWordWrap)        {            Encoding enc = Encoding.GetEncoding(Charset);            byte[] buffer = enc.GetBytes(SourceString);            string strContent = Convert.ToBase64String(buffer);            StringBuilder strTemp = new StringBuilder();            int ii = 0;            for (int i = 0; i <= strContent.Length / 76 - 1; i++)            {                strTemp.Append(strContent.Substring(76 * i, 76) + "\r\n");                ii++;            }            strTemp.Append(strContent.Substring(76 * (ii)));            strContent = strTemp.ToString();            return strContent;        }        private string ConvertStringEncoding(string SourceString, string Charset)        {            try            {                Encoding enc;                if (Charset == "8bit" || Charset == "")                {                    enc = Encoding.Default;                }                else                {                    enc = Encoding.GetEncoding(Charset);                }                return enc.GetString(Encoding.ASCII.GetBytes(SourceString));            }            catch            {                return Encoding.Default.GetString(Encoding.ASCII.GetBytes(SourceString));            }        }        //单击删除信件按钮触发的事件        private void buttonDelete_Click(object sender, EventArgs e)        {            string parameter = listBoxOperation.SelectedItem.ToString();            parameter = parameter.Substring(1, parameter.IndexOf("封") - 1);            SendToServer("DELE " + parameter);            string str = GetResponse();            if (CheckResponse(str) == false) return;            richTextBoxOriginalMail.Clear();            int j = listBoxOperation.SelectedIndex;            listBoxOperation.Items.Remove(listBoxOperation.Items[j].ToString());            MessageBox.Show("删除成功");        }    }}