1 引言

电子邮件介绍

电子邮件(简称E-mail)又称电子信箱、电子邮政，它是一种用电子手段提供信息交换的通信方式。它是全球多种网络上使用最普遍的一项服务。这种非交互式的通信,加速了信息的交流及数据传送,它是一个简易、快速的方法。通过连接全世界的Internet,实现各类信号的传送、接收、存贮等处理,将邮件送到世界的各个角落。到目前为止,可以说电子邮件是Internet资源使用最多的一种服务，E-mai1不只局限于信件的传递,还可用来传递文件、声音及图形、图像等不同类型的信息。

电子邮件不是一种“终端到终端”的服务,是被称为“存贮转发式”服务。这正是电子信箱系统的核心，利用存贮转发可进行非实时通信，属异步通信方式。即信件发送者可随时随地发送邮件，不要求接收者同时在场，即使对方现在不在，仍可将邮件立刻送到对方的信箱内,且存储在对方的电子邮箱中。接收者可在他认为方便的时候读取信件,不受时空限制。在这里,“发送”邮件意味着将邮件放到收件人的信箱中,而“接收”邮件则意味着从自己的信箱中读取信件,信箱实际上是由文件管理系统支持的一个实体。因为电子邮件是通过邮件服务器(mai1server)来传递档的。通常mailserver是执行多任务操作系统UNIX的计算机，它提供24小时的电子邮件服务,用户只要向 mail server管理人员申请一个信箱账号,就可使用这项快速的邮件服务。

电子邮件的工作原理：

电子邮件系统是一种新型的信息系统,是通信技术和计算机技术结合的产物。电子邮件的传输是通过电子邮件简单传输协议(Simple Mail Transfer Protocol,简称SMTP)这一系统软件来完成的,它是Internet下的一种电子邮件通信协议。
电子邮件的基本原理,是在通信网上设立“电子信箱系统”，它实际上是一个计算机系统。系统的硬件是一个高性能、大容量的计算机。硬盘作为信箱的存储介质,在硬盘上为用户分一定的存储空间作为用户的“信箱”，每位用户都有属于自己的—个电子信箱。并确定—个用户名和用户可以自己随意修改的口令。存储空间包含存放所收信件、编辑信件以及信件存盘三部分空间,用户使用口令开启自己的信箱,并进行发信、读信、编辑、转发、存档等各种操作。系统功能主要由软件实现。
电子邮件的通信是在信箱之间进行的。用户首先开启自己的信箱，然后通过键入命令的方式将需要发送的邮件发到对方的信箱中。邮件在信箱之间进行传递和交换,也可以与另—个邮件系统进行传递和交换。收方在取信时，使用特定账号从信箱提取。

2 代码实现部分

2.1 新建邮件帮助类，自由命名即可，这里以Utilities_Xofly为例

邮件帮助类也可以在这里查看：SmtpServerHelper

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net.Mail;
using System.Net.Sockets;
using System.Text;
using System.Threading.Tasks;
using System.Collections;namespace Sea.Common
{public class Utilities_Xofly{public enum MailFormat { Text, HTML };public enum MailPriority { Low = 1, Normal = 3, High = 5 };/// <summary>  /// 添加附件  /// </summary>  public class MailAttachments{#region 构造函数  public MailAttachments(){_Attachments = new ArrayList();}#endregion#region 私有字段  private IList _Attachments;private const int MaxAttachmentNum = 10;#endregion#region 索引器  public string this[int index]{get { return (string)_Attachments[index]; }}#endregion#region 公共方法  /// <summary>  /// 添加邮件附件  /// </summary>  /// <param name="FilePath">附件的绝对路径</param>  public void Add(params string[] filePath){if (filePath == null){throw (new ArgumentNullException("非法的附件"));}else{for (int i = 0; i < filePath.Length; i++){Add(filePath[i]);}}}/// <summary>  /// 添加一个附件,当指定的附件不存在时，忽略该附件，不产生异常。  /// </summary>  /// <param name="filePath">附件的绝对路径</param>  public void Add(string filePath){if (System.IO.File.Exists(filePath)){if (_Attachments.Count < MaxAttachmentNum){_Attachments.Add(filePath);}}}/// <summary>  /// 清除所有附件  /// </summary>  public void Clear(){_Attachments.Clear();}/// <summary>  /// 获取附件个数  /// </summary>  public int Count{get { return _Attachments.Count; }}#endregion}/// <summary>  /// 邮件信息  /// </summary>  public class MailMessage{#region 构造函数  public MailMessage(){_Recipients = new ArrayList();        //收件人列表  _Attachments = new MailAttachments(); //附件  _BodyFormat = MailFormat.HTML;        //缺省的邮件格式为HTML  _Priority = MailPriority.Normal;_Charset = "GB2312";}#endregion#region 私有字段  private int _MaxRecipientNum = 30;private string _From;      //发件人地址  private string _FromName;  //发件人姓名  private IList _Recipients; //收件人  private MailAttachments _Attachments;//附件  private string _Body;      //内容  private string _Subject;   //主题  private MailFormat _BodyFormat;     //邮件格式  private string _Charset = "GB2312"; //字符编码格式  private MailPriority _Priority;     //邮件优先级  #endregion#region 公有属性  /// <summary>  /// 设定语言代码，默认设定为GB2312，如不需要可设置为""  /// </summary>  public string Charset{get { return _Charset; }set { _Charset = value; }}/// <summary>  /// 最大收件人  /// </summary>  public int MaxRecipientNum{get { return _MaxRecipientNum; }set { _MaxRecipientNum = value; }}/// <summary>  /// 发件人地址  /// </summary>  public string From{get { return _From; }set { _From = value; }}/// <summary>  /// 发件人姓名  /// </summary>  public string FromName{get { return _FromName; }set { _FromName = value; }}/// <summary>  /// 内容  /// </summary>  public string Body{get { return _Body; }set { _Body = value; }}/// <summary>  /// 主题  /// </summary>  public string Subject{get { return _Subject; }set { _Subject = value; }}/// <summary>  /// 附件  /// </summary>  public MailAttachments Attachments{get { return _Attachments; }set { _Attachments = value; }}/// <summary>  /// 优先权  /// </summary>  public MailPriority Priority{get { return _Priority; }set { _Priority = value; }}/// <summary>  /// 收件人  /// </summary>  public IList Recipients{get { return _Recipients; }}/// <summary>  /// 邮件格式  /// </summary>  public MailFormat BodyFormat{set { _BodyFormat = value; }get { return _BodyFormat; }}#endregion#region 公共方法  /// <summary>  /// 增加一个收件人地址  /// </summary>  /// <param name="recipient">收件人的Email地址</param>  public void AddRecipients(string recipient){if (_Recipients.Count < MaxRecipientNum){_Recipients.Add(recipient);}}/// <summary>  /// 增加多个收件人地址  /// </summary>  /// <param name="recipient">收件人的Email地址集合</param>  public void AddRecipients(params string[] recipient){if (recipient == null){throw (new ArgumentException("收件人不能为空."));}else{for (int i = 0; i < recipient.Length; i++){AddRecipients(recipient[i]);}}}#endregion}/// <summary>  /// 邮件操作  /// </summary>  public class SmtpServerHelper{#region 构造函数、析构函数  public SmtpServerHelper(){SMTPCodeAdd();}~SmtpServerHelper(){networkStream.Close();tcpClient.Close();}#endregion#region 私有字段  /// <summary>  /// 回车换行  /// </summary>  private string CRLF = "\r\n";/// <summary>  /// 错误消息反馈  /// </summary>  private string errmsg;/// <summary>  /// TcpClient对象，用于连接服务器  /// </summary>   private TcpClient tcpClient;/// <summary>  /// NetworkStream对象  /// </summary>   private NetworkStream networkStream;/// <summary>  /// 服务器交互记录  /// </summary>  private string logs = "";/// <summary>  /// SMTP错误代码哈希表  /// </summary>  private Hashtable ErrCodeHT = new Hashtable();/// <summary>  /// SMTP正确代码哈希表  /// </summary>  private Hashtable RightCodeHT = new Hashtable();#endregion#region 公有属性  /// <summary>  /// 错误消息反馈  /// </summary>  public string ErrMsg{set { errmsg = value; }get { return errmsg; }}#endregion#region 私有方法  /// <summary>  /// 将字符串编码为Base64字符串  /// </summary>  /// <param name="str">要编码的字符串</param>  private string Base64Encode(string str){byte[] barray;barray = Encoding.Default.GetBytes(str);return Convert.ToBase64String(barray);}/// <summary>  /// 将Base64字符串解码为普通字符串  /// </summary>  /// <param name="str">要解码的字符串</param>  private string Base64Decode(string str){byte[] barray;barray = Convert.FromBase64String(str);return Encoding.Default.GetString(barray);}/// <summary>  /// 得到上传附件的文件流  /// </summary>  /// <param name="FilePath">附件的绝对路径</param>  private string GetStream(string FilePath){System.IO.FileStream FileStr = new System.IO.FileStream(FilePath, System.IO.FileMode.Open);byte[] by = new byte[System.Convert.ToInt32(FileStr.Length)];FileStr.Read(by, 0, by.Length);FileStr.Close();return (System.Convert.ToBase64String(by));}/// <summary>  /// SMTP回应代码哈希表  /// </summary>  private void SMTPCodeAdd(){ErrCodeHT.Add("421", "服务未就绪，关闭传输信道");ErrCodeHT.Add("432", "需要一个密码转换");ErrCodeHT.Add("450", "要求的邮件操作未完成，邮箱不可用（例如，邮箱忙）");ErrCodeHT.Add("451", "放弃要求的操作；处理过程中出错");ErrCodeHT.Add("452", "系统存储不足，要求的操作未执行");ErrCodeHT.Add("454", "临时认证失败");ErrCodeHT.Add("500", "邮箱地址错误");ErrCodeHT.Add("501", "参数格式错误");ErrCodeHT.Add("502", "命令不可实现");ErrCodeHT.Add("503", "服务器需要SMTP验证");ErrCodeHT.Add("504", "命令参数不可实现");ErrCodeHT.Add("530", "需要认证");ErrCodeHT.Add("534", "认证机制过于简单");ErrCodeHT.Add("538", "当前请求的认证机制需要加密");ErrCodeHT.Add("550", "要求的邮件操作未完成，邮箱不可用（例如，邮箱未找到，或不可访问）");ErrCodeHT.Add("551", "用户非本地，请尝试<forward-path>");ErrCodeHT.Add("552", "过量的存储分配，要求的操作未执行");ErrCodeHT.Add("553", "邮箱名不可用，要求的操作未执行（例如邮箱格式错误）");ErrCodeHT.Add("554", "传输失败");RightCodeHT.Add("220", "服务就绪");RightCodeHT.Add("221", "服务关闭传输信道");RightCodeHT.Add("235", "验证成功");RightCodeHT.Add("250", "要求的邮件操作完成");RightCodeHT.Add("251", "非本地用户，将转发向<forward-path>");RightCodeHT.Add("334", "服务器响应验证Base64字符串");RightCodeHT.Add("354", "开始邮件输入，以<CRLF>.<CRLF>结束");}/// <summary>  /// 发送SMTP命令  /// </summary>   private bool SendCommand(string str){byte[] WriteBuffer;if (str == null || str.Trim() == String.Empty){return true;}logs += str;WriteBuffer = Encoding.Default.GetBytes(str);try{networkStream.Write(WriteBuffer, 0, WriteBuffer.Length);}catch{errmsg = "网络连接错误";return false;}return true;}/// <summary>  /// 接收SMTP服务器回应  /// </summary>  private string RecvResponse(){int StreamSize;string Returnvalue = String.Empty;byte[] ReadBuffer = new byte[1024];try{StreamSize = networkStream.Read(ReadBuffer, 0, ReadBuffer.Length);}catch{errmsg = "网络连接错误";return "false";}if (StreamSize == 0){return Returnvalue;}else{Returnvalue = Encoding.Default.GetString(ReadBuffer).Substring(0, StreamSize);logs += Returnvalue + this.CRLF;return Returnvalue;}}/// <summary>  /// 与服务器交互，发送一条命令并接收回应。  /// </summary>  /// <param name="str">一个要发送的命令</param>  /// <param name="errstr">如果错误，要反馈的信息</param>  private bool Dialog(string str, string errstr){if (str == null || str.Trim() == string.Empty){return true;}if (SendCommand(str)){string RR = RecvResponse();if (RR == "false"){return false;}//检查返回的代码，根据[RFC 821]返回代码为3位数字代码如220  string RRCode = RR.Substring(0, 3);if (RightCodeHT[RRCode] != null){return true;}else{if (ErrCodeHT[RRCode] != null){errmsg += (RRCode + ErrCodeHT[RRCode].ToString());errmsg += CRLF;}else{errmsg += RR;}errmsg += errstr;return false;}}else{return false;}}/// <summary>  /// 与服务器交互，发送一组命令并接收回应。  /// </summary>  private bool Dialog(string[] str, string errstr){for (int i = 0; i < str.Length; i++){if (!Dialog(str[i], "")){errmsg += CRLF;errmsg += errstr;return false;}}return true;}/// <summary>  /// 连接服务器  /// </summary>  private bool Connect(string smtpServer, int port){try{tcpClient = new TcpClient(smtpServer, port);}catch (Exception e){errmsg = e.ToString();return false;}networkStream = tcpClient.GetStream();if (RightCodeHT[RecvResponse().Substring(0, 3)] == null){errmsg = "网络连接失败";return false;}return true;}/// <summary>  /// 获取优先级  /// </summary>  /// <param name="mailPriority">优先级</param>  private string GetPriorityString(MailPriority mailPriority){string priority = "Normal";if (mailPriority == MailPriority.Low){priority = "Low";}else if (mailPriority == MailPriority.High){priority = "High";}return priority;}/// <summary>  /// 发送电子邮件  /// </summary>  /// <param name="smtpServer">发信SMTP服务器</param>  /// <param name="port">端口，默认为25</param>  /// <param name="username">发信人邮箱地址</param>  /// <param name="password">发信人邮箱密码</param>  /// <param name="mailMessage">邮件内容</param>  private bool SendEmail(string smtpServer, int port, bool ESmtp, string username, string password, MailMessage mailMessage){if (Connect(smtpServer, port) == false) return false;string priority = GetPriorityString(mailMessage.Priority);bool Html = (mailMessage.BodyFormat == MailFormat.HTML);string[] SendBuffer;string SendBufferstr;//进行SMTP验证  if (ESmtp){SendBuffer = new String[4];SendBuffer[0] = "EHLO " + smtpServer + CRLF;SendBuffer[1] = "AUTH LOGIN" + CRLF;SendBuffer[2] = Base64Encode(username) + CRLF;SendBuffer[3] = Base64Encode(password) + CRLF;if (!Dialog(SendBuffer, "SMTP服务器验证失败，请核对用户名和密码。")) return false;}else{SendBufferstr = "HELO " + smtpServer + CRLF;if (!Dialog(SendBufferstr, "")) return false;}//发件人地址  SendBufferstr = "MAIL FROM:<" + username + ">" + CRLF;if (!Dialog(SendBufferstr, "发件人地址错误，或不能为空")) return false;//收件人地址  SendBuffer = new string[mailMessage.Recipients.Count];for (int i = 0; i < mailMessage.Recipients.Count; i++){SendBuffer[i] = "RCPT TO:<" + (string)mailMessage.Recipients[i] + ">" + CRLF;}if (!Dialog(SendBuffer, "收件人地址有误")) return false;SendBufferstr = "DATA" + CRLF;if (!Dialog(SendBufferstr, "")) return false;//发件人姓名  SendBufferstr = "From:" + mailMessage.FromName + "<" + mailMessage.From + ">" + CRLF;if (mailMessage.Recipients.Count == 0){return false;}else{SendBufferstr += "To:=?" + mailMessage.Charset.ToUpper() + "?B?" + Base64Encode((string)mailMessage.Recipients[0]) + "?=" + "<" + (string)mailMessage.Recipients[0] + ">" + CRLF;}SendBufferstr += ((mailMessage.Subject == String.Empty || mailMessage.Subject == null) ? "Subject:" : ((mailMessage.Charset == "") ? ("Subject:" + mailMessage.Subject) : ("Subject:" + "=?" + mailMessage.Charset.ToUpper() + "?B?" + Base64Encode(mailMessage.Subject) + "?="))) + CRLF;SendBufferstr += "X-Priority:" + priority + CRLF;SendBufferstr += "X-MSMail-Priority:" + priority + CRLF;SendBufferstr += "Importance:" + priority + CRLF;SendBufferstr += "X-Mailer: Lion.Web.Mail.SmtpMail Pubclass [cn]" + CRLF;SendBufferstr += "MIME-Version: 1.0" + CRLF;if (mailMessage.Attachments.Count != 0){SendBufferstr += "Content-Type: multipart/mixed;" + CRLF;SendBufferstr += " boundary=\"=====" + (Html ? "001_Dragon520636771063_" : "001_Dragon303406132050_") + "=====\"" + CRLF + CRLF;}if (Html){if (mailMessage.Attachments.Count == 0){SendBufferstr += "Content-Type: multipart/alternative;" + CRLF; //内容格式和分隔符  SendBufferstr += " boundary=\"=====003_Dragon520636771063_=====\"" + CRLF + CRLF;SendBufferstr += "This is a multi-part message in MIME format." + CRLF + CRLF;}else{SendBufferstr += "This is a multi-part message in MIME format." + CRLF + CRLF;SendBufferstr += "--=====001_Dragon520636771063_=====" + CRLF;SendBufferstr += "Content-Type: multipart/alternative;" + CRLF; //内容格式和分隔符  SendBufferstr += " boundary=\"=====003_Dragon520636771063_=====\"" + CRLF + CRLF;}SendBufferstr += "--=====003_Dragon520636771063_=====" + CRLF;SendBufferstr += "Content-Type: text/plain;" + CRLF;SendBufferstr += ((mailMessage.Charset == "") ? (" charset=\"iso-8859-1\"") : (" charset=\"" + mailMessage.Charset.ToLower() + "\"")) + CRLF;SendBufferstr += "Content-Transfer-Encoding: base64" + CRLF + CRLF;SendBufferstr += Base64Encode("邮件内容为HTML格式，请选择HTML方式查看") + CRLF + CRLF;SendBufferstr += "--=====003_Dragon520636771063_=====" + CRLF;SendBufferstr += "Content-Type: text/html;" + CRLF;SendBufferstr += ((mailMessage.Charset == "") ? (" charset=\"iso-8859-1\"") : (" charset=\"" + mailMessage.Charset.ToLower() + "\"")) + CRLF;SendBufferstr += "Content-Transfer-Encoding: base64" + CRLF + CRLF;SendBufferstr += Base64Encode(mailMessage.Body) + CRLF + CRLF;SendBufferstr += "--=====003_Dragon520636771063_=====--" + CRLF;}else{if (mailMessage.Attachments.Count != 0){SendBufferstr += "--=====001_Dragon303406132050_=====" + CRLF;}SendBufferstr += "Content-Type: text/plain;" + CRLF;SendBufferstr += ((mailMessage.Charset == "") ? (" charset=\"iso-8859-1\"") : (" charset=\"" + mailMessage.Charset.ToLower() + "\"")) + CRLF;SendBufferstr += "Content-Transfer-Encoding: base64" + CRLF + CRLF;SendBufferstr += Base64Encode(mailMessage.Body) + CRLF;}if (mailMessage.Attachments.Count != 0){for (int i = 0; i < mailMessage.Attachments.Count; i++){string filepath = (string)mailMessage.Attachments[i];SendBufferstr += "--=====" + (Html ? "001_Dragon520636771063_" : "001_Dragon303406132050_") + "=====" + CRLF;SendBufferstr += "Content-Type: text/plain;" + CRLF;SendBufferstr += " name=\"=?" + mailMessage.Charset.ToUpper() + "?B?" + Base64Encode(filepath.Substring(filepath.LastIndexOf("\\") + 1)) + "?=\"" + CRLF;SendBufferstr += "Content-Transfer-Encoding: base64" + CRLF;SendBufferstr += "Content-Disposition: attachment;" + CRLF;SendBufferstr += " filename=\"=?" + mailMessage.Charset.ToUpper() + "?B?" + Base64Encode(filepath.Substring(filepath.LastIndexOf("\\") + 1)) + "?=\"" + CRLF + CRLF;SendBufferstr += GetStream(filepath) + CRLF + CRLF;}SendBufferstr += "--=====" + (Html ? "001_Dragon520636771063_" : "001_Dragon303406132050_") + "=====--" + CRLF + CRLF;}SendBufferstr += CRLF + "." + CRLF;if (!Dialog(SendBufferstr, "错误信件信息")) return false;SendBufferstr = "QUIT" + CRLF;if (!Dialog(SendBufferstr, "断开连接时错误")) return false;networkStream.Close();tcpClient.Close();return true;}#endregion#region 公有方法  /// <summary>  /// 发送电子邮件,SMTP服务器不需要身份验证  /// </summary>  /// <param name="smtpServer">发信SMTP服务器</param>  /// <param name="port">端口，默认为25</param>  /// <param name="mailMessage">邮件内容</param>  public bool SendEmail(string smtpServer, int port, MailMessage mailMessage){return SendEmail(smtpServer, port, false, "", "", mailMessage);}/// <summary>  /// 发送电子邮件,SMTP服务器需要身份验证  /// </summary>  /// <param name="smtpServer">发信SMTP服务器</param>  /// <param name="port">端口，默认为25</param>  /// <param name="username">发信人邮箱地址</param>  /// <param name="password">发信人邮箱密码</param>  /// <param name="mailMessage">邮件内容</param>  public bool SendEmail(string smtpServer, int port, string username, string password, MailMessage mailMessage){return SendEmail(smtpServer, port, true, username, password, mailMessage);}#endregion}/// <summary>  /// 发送邮件  /// </summary>  //--------------------调用-----------------------  //MailAttachments ma=new MailAttachments();  //ma.Add(@"附件地址");  //MailMessage mail = new MailMessage();  //mail.Attachments=ma;  //mail.Body="你好";  //mail.AddRecipients("zjy99684268@163.com");  //mail.From="zjy99684268@163.com";  //mail.FromName="zjy";  //mail.Subject="Hello";  //SmtpClient sp = new SmtpClient();  //sp.SmtpServer = "smtp.163.com";  //sp.Send(mail, "zjy99684268@163.com", "123456");  //------------------------------------------------  public class SmtpClient{#region 构造函数  public SmtpClient(){ }public SmtpClient(string _smtpServer){_SmtpServer = _smtpServer;}#endregion#region 私有字段  private string errmsg;private string _SmtpServer;#endregion#region 公有属性  /// <summary>  /// 错误消息反馈  /// </summary>  public string ErrMsg{get { return errmsg; }}/// <summary>  /// 邮件服务器  /// </summary>  public string SmtpServer{set { _SmtpServer = value; }get { return _SmtpServer; }}#endregionpublic bool Send(MailMessage mailMessage, string username, string password){SmtpServerHelper helper = new SmtpServerHelper();if (helper.SendEmail(_SmtpServer, 25, username, password, mailMessage))return true;else{errmsg = helper.ErrMsg;return false;}}}/// <summary>  /// 操作服务器上邮件  /// </summary>  public class SmtpMail{public SmtpMail(){ }#region 字段  private StreamReader sr;private StreamWriter sw;private TcpClient tcpClient;private NetworkStream networkStream;#endregion#region 私有方法  /// <summary>  /// 向服务器发送信息  /// </summary>  private bool SendDataToServer(string str){try{sw.WriteLine(str);sw.Flush();return true;}catch (Exception err){return false;}}/// <summary>  /// 从网络流中读取服务器回送的信息  /// </summary>  private string ReadDataFromServer(){string str = null;try{str = sr.ReadLine();if (str[0] == '-'){str = null;}}catch (Exception err){str = err.Message;}return str;}#endregion#region 获取邮件信息  /// <summary>  /// 获取邮件信息  /// </summary>  /// <param name="uid">邮箱账号</param>  /// <param name="pwd">邮箱密码</param>  /// <returns>邮件信息</returns>  public ArrayList ReceiveMail(string uid, string pwd){ArrayList EmailMes = new ArrayList();string str;int index = uid.IndexOf('@');string pop3Server = "pop3." + uid.Substring(index + 1);tcpClient = new TcpClient(pop3Server, 110);networkStream = tcpClient.GetStream();sr = new StreamReader(networkStream);sw = new StreamWriter(networkStream);if (ReadDataFromServer() == null) return EmailMes;if (SendDataToServer("USER " + uid) == false) return EmailMes;if (ReadDataFromServer() == null) return EmailMes;if (SendDataToServer("PASS " + pwd) == false) return EmailMes;if (ReadDataFromServer() == null) return EmailMes;if (SendDataToServer("LIST") == false) return EmailMes;if ((str = ReadDataFromServer()) == null) return EmailMes;string[] splitString = str.Split(' ');int count = int.Parse(splitString[1]);if (count > 0){for (int i = 0; i < count; i++){if ((str = ReadDataFromServer()) == null) return EmailMes;splitString = str.Split(' ');EmailMes.Add(string.Format("第{0}封邮件，{1}字节", splitString[0], splitString[1]));}return EmailMes;}else{return EmailMes;}}#endregion#region 读取邮件内容  /// <summary>  /// 读取邮件内容  /// </summary>  /// <param name="mailMessage">第几封</param>  /// <returns>内容</returns>  public string ReadEmail(string str){string state = "";if (SendDataToServer("RETR " + str) == false)state = "Error";else{state = sr.ReadToEnd();}return state;}#endregion#region 删除邮件  /// <summary>  /// 删除邮件  /// </summary>  /// <param name="str">第几封</param>  /// <returns>操作信息</returns>  public string DeleteEmail(string str){string state = "";if (SendDataToServer("DELE " + str) == true){state = "成功删除";}else{state = "Error";}return state;}#endregion#region 关闭服务器连接  /// <summary>  /// 关闭服务器连接  /// </summary>  public void CloseConnection(){SendDataToServer("QUIT");sr.Close();sw.Close();networkStream.Close();tcpClient.Close();}#endregion}}
}

2.2 方法的调用

方法调用查看如下所示的样例，mail.AddRecipients()方法，如果需要发送多个邮箱的时候传入数组即可。

        /// <summary>  /// 发送邮件  /// </summary>  //--------------------调用-----------------------  //MailAttachments ma=new MailAttachments();  //ma.Add(@"附件地址");  //MailMessage mail = new MailMessage();  //mail.Attachments=ma;  //mail.Body="你好";  //mail.AddRecipients("zjy99684268@163.com");  //mail.From="zjy99684268@163.com";  //mail.FromName="zjy";  //mail.Subject="Hello";  //SmtpClient sp = new SmtpClient();  //sp.SmtpServer = "smtp.163.com";  //sp.Send(mail, "zjy99684268@163.com", "123456");  //------------------------------------------------

2.3 查看相关邮箱的设置（这里以QQ邮箱为例）

点击查看POP3/SMTP服务，记得一定要开启哦，开启之后如下图所示。

2.4 运行相关程序，查看邮件内容是否正确

邮件发送成功之后登录到对应的接收邮箱查看邮件内容是否正确。

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