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以下部份可借鉴，据说有错误，改成功的朋友请指出错误，谢谢！！原文出处http://www.cnblogs.com/mingmingruyuedlut/archive/2011/10/14/2212255.html
Ø 发送邮件所用的核心知识点
Ø 具体代码请看如下所示：
using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Net.Mail;using System.Net.Mime;using System.IO;using System.Timers;using System.Xml;namespace MyEmailTest{ class Program { static void Main(string[] args) { try { //smtp.163.com string senderServerIp = "123.125.50.133"; //smtp.gmail.com //string senderServerIp = "74.125.127.109"; //smtp.qq.com //string senderServerIp = "58.251.149.147"; //string senderServerIp = "smtp.sina.com"; string toMailAddress = "mingmingruyuedlut@163.com"; string fromMailAddress = "mingmingruyuedlut@163.com"; string subjectInfo = "Test sending e_mail"; string bodyInfo = "Hello Eric, This is my first testing e_mail"; string mailUsername = "mingmingruyuedlut"; string mailPassword = ".........."; //发送邮箱的密码（） string mailPort = "25"; string attachPath = "E:\\123123.txt; E:\\haha.pdf"; MyEmail email = new MyEmail(senderServerIp, toMailAddress, fromMailAddress, subjectInfo, bodyInfo, mailUsername, mailPassword, mailPort, false, false); email.AddAttachments(attachPath); email.Send(); } catch (Exception ex) { Console.WriteLine(ex.ToString()); } } } public class MyEmail { private MailMessage mMailMessage; //主要处理发送邮件的内容（如：收发人地址、标题、主体、图片等等） private SmtpClient mSmtpClient; //主要处理用smtp方式发送此邮件的配置信息（如：邮件服务器、发送端口号、验证方式等等） private int mSenderPort; //发送邮件所用的端口号（htmp协议默认为25） private string mSenderServerHost; //发件箱的邮件服务器地址（IP形式或字符串形式均可） private string mSenderPassword; //发件箱的密码 private string mSenderUsername; //发件箱的用户名（即@符号前面的字符串，例如：hello@163.com，用户名为：hello） private bool mEnableSsl; //是否对邮件内容进行socket层加密传输 private bool mEnablePwdAuthentication; //是否对发件人邮箱进行密码验证 /// /// 构造函数 /// ///发件箱的邮件服务器地址 ///收件人地址（可以是多个收件人，程序中是以“;"进行区分的） ///发件人地址 ///邮件标题 ///邮件内容（可以以html格式进行设计） ///发件箱的用户名（即@符号前面的字符串，例如：hello@163.com，用户名为：hello） ///发件人邮箱密码 ///发送邮件所用的端口号（htmp协议默认为25） ///true表示对邮件内容进行socket层加密传输，false表示不加密 ///true表示对发件人邮箱进行密码验证，false表示不对发件人邮箱进行密码验证 public MyEmail(string server, string toMail, string fromMail, string subject, string emailBody, string username, string password, string port, bool sslEnable, bool pwdCheckEnable) { try { mMailMessage = new MailMessage(); mMailMessage.To.Add(toMail); mMailMessage.From = new MailAddress(fromMail); mMailMessage.Subject = subject; mMailMessage.Body = emailBody; mMailMessage.IsBodyHtml = true; mMailMessage.BodyEncoding = System.Text.Encoding.UTF8; mMailMessage.Priority = MailPriority.Normal; this.mSenderServerHost = server; this.mSenderUsername = username; this.mSenderPassword = password; this.mSenderPort = Convert.ToInt32(port); this.mEnableSsl = sslEnable; this.mEnablePwdAuthentication = pwdCheckEnable; } catch (Exception ex) { Console.WriteLine(ex.ToString()); } } /// /// 添加附件 /// ///附件的路径集合，以分号分隔 public void AddAttachments(string attachmentsPath) { try { string[] path = attachmentsPath.Split(';'); //以什么符号分隔可以自定义 Attachment data; ContentDisposition disposition; for (int i = 0; i < path.Length; i++) { data = new Attachment(path[i], MediaTypeNames.Application.Octet); disposition = data.ContentDisposition; disposition.CreationDate = File.GetCreationTime(path[i]); disposition.ModificationDate = File.GetLastWriteTime(path[i]); disposition.ReadDate = File.GetLastAccessTime(path[i]); mMailMessage.Attachments.Add(data); } } catch (Exception ex) { Console.WriteLine(ex.ToString()); } } /// /// 邮件的发送 /// public void Send() { try { if (mMailMessage != null) { mSmtpClient = new SmtpClient(); //mSmtpClient.Host = "smtp." + mMailMessage.From.Host; mSmtpClient.Host = this.mSenderServerHost; mSmtpClient.Port = this.mSenderPort; mSmtpClient.UseDefaultCredentials = false; mSmtpClient.EnableSsl = this.mEnableSsl; if (this.mEnablePwdAuthentication) { System.Net.NetworkCredential nc = new System.Net.NetworkCredential(this.mSenderUsername, this.mSenderPassword); //mSmtpClient.Credentials = new System.Net.NetworkCredential(this.mSenderUsername, this.mSenderPassword); //NTLM: Secure Password Authentication in Microsoft Outlook Express mSmtpClient.Credentials = nc.GetCredential(mSmtpClient.Host, mSmtpClient.Port, "NTLM"); } else { mSmtpClient.Credentials = new System.Net.NetworkCredential(this.mSenderUsername, this.mSenderPassword); } mSmtpClient.DeliveryMethod = System.Net.Mail.SmtpDeliveryMethod.Network; mSmtpClient.Send(mMailMessage); } } catch (Exception ex) { Console.WriteLine(ex.ToString()); } } }}