public class MailUtil
   {
       static MailUtil()
       {
           //
           // TODO: 在此处添加构造函数逻辑
           //
       }

       //读取指定URL地址的HTML，用来以后发送网页用
       public static string ScreenScrapeHtml(string url)
       {
           StreamReader reader = new StreamReader(System.Net.WebRequest.Create(url).GetResponse().GetResponseStream());
           string str = reader.ReadToEnd();
           reader.Close();
           return str;
       }

       ///   <summary>
       ///   发送邮件
       ///   </summary>
       ///   <param   name= "server "> smtp地址 </param>
       ///   <param   name= "username "> 用户名 </param>
       ///   <param   name= "password "> 密码 </param>
       ///   <param   name= "from "> 发信人地址 </param>
       ///   <param   name= "to "> 收信人地址 </param>
       ///   <param   name= "subject "> 邮件标题 </param>
       ///   <param   name= "body "> 邮件正文 </param>
       ///    <param   name= "IsHtml "> 是否是HTML格式的邮件 </param>
       public static void SendMail(string from, string to, string subject, string body, string server, string username, string password, bool IsHtml)
       {
           //设置SMTP 验证
         
           SmtpClient mailClient = new SmtpClient(server);

           //表示当前登陆用户的默认凭据进行身份验证，并且包含用户名密码
           mailClient.UseDefaultCredentials = true;
           mailClient.Credentials = new System.Net.NetworkCredential(username, password);

           //指定如何发送电子邮件。
           //Network         电子邮件通过网络发送到   SMTP   服务器。    
           //PickupDirectoryFromIis   将电子邮件复制到挑选目录，然后通过本地   Internet   信息服务   (IIS)   传送。    
           //SpecifiedPickupDirectory 将电子邮件复制到 SmtpClient.PickupDirectoryLocation 属性指定的目录，然后由外部应用程序传送。   

           mailClient.DeliveryMethod = System.Net.Mail.SmtpDeliveryMethod.Network;

           //创建邮件对象
           MailMessage mailMessage = new MailMessage(from, to, subject, body);
          

           //定义邮件正文，主题的编码方式
           mailMessage.BodyEncoding = System.Text.Encoding.GetEncoding("gb2312");
           mailMessage.SubjectEncoding = System.Text.Encoding.GetEncoding("gb2312");

           //获取或者设置一个值，该值表示电子邮件正文是否为HTML
           mailMessage.IsBodyHtml = IsHtml;

           //指定邮件的优先级
           mailMessage.Priority = MailPriority.Normal;

 

           string strFileName = @"f:/att.txt";

           if (strFileName != " " && strFileName != null)
           {
               Attachment data = new Attachment(strFileName);
               mailMessage.Attachments.Add(data);
           }
           

           //发件人身份验证,否则163   发不了
           mailClient.Credentials = new System.Net.NetworkCredential(username, password);

           //发送
           mailClient.Send(mailMessage);
       }

       //发送plaintxt
       public static void SendText(string from, string to, string subject, string body, string server, string username, string password)
       {
           SendMail(from, to,subject,body,server, username, password, false);
       }

       //发送HTML内容
       public static void SendHtml(string from, string to, string subject, string body, string server, string username, string password)
       {
           SendMail(from, to, subject, body, server, username, password, true);
       }

       //发送制定网页
       public static void SendWebUrl(string from, string to, string subject, string body, string server, string username, string password, string url)
       {
           //发送制定网页
           SendHtml(from, to, subject, ScreenScrapeHtml(url), server, username, password);

       }
   }