邮件有需要加密的地方，提供一个加密方法类

public static class DesSet

{     /// <summary>     /// 加密方法 Key 必须为8位     /// </summary>     /// <param name="pToEncrypt"></param>     /// <param name="sKey"></param>     /// <returns></returns>     public static string Encrypt(string pToEncrypt, string sKey)     {         DESCryptoServiceProvider des = new DESCryptoServiceProvider();

        byte[] inputByteArray = Encoding.Default.GetBytes(pToEncrypt);

        des.Key = ASCIIEncoding.ASCII.GetBytes(sKey);         des.IV = ASCIIEncoding.ASCII.GetBytes(sKey);         MemoryStream ms = new MemoryStream();         CryptoStream cs = new CryptoStream(ms, des.CreateEncryptor(), CryptoStreamMode.Write);         cs.Write(inputByteArray, 0, inputByteArray.Length);         cs.FlushFinalBlock();         StringBuilder ret = new StringBuilder();         foreach (byte b in ms.ToArray())         {             ret.AppendFormat("{0:X2}", b);         }         ret.ToString();         return ret.ToString();     }     /// <summary>     /// 解密方法 Key 必须为8位     /// </summary>     /// <param name="pToDecrypt"></param>     /// <param name="sKey"></param>     /// <returns></returns>     public static string Decrypt(string pToDecrypt, string sKey)     {         try         {             DESCryptoServiceProvider des = new DESCryptoServiceProvider();             byte[] inputByteArray = new byte[pToDecrypt.Length / 2];             for (int x = 0; x < pToDecrypt.Length / 2; x++)             {                 int i = (Convert.ToInt32(pToDecrypt.Substring(x * 2, 2), 16));                 inputByteArray[x] = (byte)i;             }             des.Key = ASCIIEncoding.ASCII.GetBytes(sKey);             des.IV = ASCIIEncoding.ASCII.GetBytes(sKey);             MemoryStream ms = new MemoryStream();             CryptoStream cs = new CryptoStream(ms, des.CreateDecryptor(), CryptoStreamMode.Write);             cs.Write(inputByteArray, 0, inputByteArray.Length);             //如果数据为空字符串会报不正确的数据             cs.FlushFinalBlock();             StringBuilder ret = new StringBuilder();             return System.Text.Encoding.Default.GetString(ms.ToArray());         }         catch         {             return null;         }     }     /// <summary>     /// 解密方法 Key 必须为8位     /// </summary>     /// <param name="pToDecrypt"></param>     /// <param name="sKey"></param>     /// <returns></returns>     public static string qxDecrypt(string pToDecrypt, string sKey)     {         DESCryptoServiceProvider des = new DESCryptoServiceProvider();         byte[] inputByteArray = new byte[pToDecrypt.Length / 2];         for (int x = 0; x < pToDecrypt.Length / 2; x++)         {             int i = (Convert.ToInt32(pToDecrypt.Substring(x * 2, 2), 16));             inputByteArray[x] = (byte)i;         }         des.Key = ASCIIEncoding.ASCII.GetBytes(sKey);         des.IV = ASCIIEncoding.ASCII.GetBytes(sKey);         MemoryStream ms = new MemoryStream();         CryptoStream cs = new CryptoStream(ms, des.CreateDecryptor(), CryptoStreamMode.Write);         cs.Write(inputByteArray, 0, inputByteArray.Length);         //如果数据为空字符串会报不正确的数据         cs.FlushFinalBlock();         StringBuilder ret = new StringBuilder();         return System.Text.Encoding.Default.GetString(ms.ToArray());     } }

********************************************************************************

群发上千封邮件，发送太快，会出现可能被服务器拒绝的情况。使用线程控制发送间隔

    protected void btn_sendMail_Click(object sender, EventArgs e)

    {         ThreadStart mailThread = new ThreadStart(SendMail);         Thread sendMail = new Thread(mailThread);         sendMail.Name = "thread send mail";         sendMail.Start();     }

    private void SendMail()

    {         Mails mySendMail = new Mails();         for (int i = 0; i < lists.Count; i++)         {             mySendMail = new Mails("nihao",lists[i].ToString(), lists[i]);             mySendMail.SendMail();             if ((i + 1) % 50 == 0)             {                 Thread.Sleep(60000);//歇一分钟再发吧。。             }         }     }

*****************************************************************

Mails类

    public void SendMail()

    {         lock (this)         {             Thread.Sleep(3000);             //创建smtpclient对象             System.Net.Mail.SmtpClient client = new SmtpClient();             client.Host = smtp;             client.UseDefaultCredentials = false;             client.Credentials = new System.Net.NetworkCredential(from,pwd);             client.DeliveryMethod = SmtpDeliveryMethod.Network;

            //创建mailMessage对象 

            System.Net.Mail.MailMessage message = new MailMessage(from,to);             message.Subject = subject;             message.SubjectEncoding = Encoding.UTF8;             message.Body = body;             message.BodyEncoding = System.Text.Encoding.UTF8;             message.IsBodyHtml = true;

            try             {                 client.Send(message);                 StreamWriter sw = new StreamWriter("c:/message.txt", true);                 sw.Write(this.to+"  发送成功" + "\r\n");                 sw.Close();             }             catch (Exception ex)             {                 StreamWriter sw = new StreamWriter("c:/message.txt", true);                 sw.Write(this.to+"  发送失败。失败原因："+ex.Message + "\r\n");                 sw.Close();             }         }     }