线程池发送邮件的方法（向多个用户发送同一邮件）

1、前台代码

<asp:Button runat="server" ID="btn_SendMail" Text="发送邮件" OnClick="btn_SendMail_Click" />

2、后台发送邮件的一个实体类

 //邮件发送参数的实体类
        public class MailsSendClass
        {
            public string EmailHost { get; set; }//邮箱SMTP 事务的主机的名称或 IP 地址
            public string EmailFrom { get; set; }//发件人邮箱
            public string EmailPwd { get; set; }//发件人邮箱密码         
            public string EmailTitle { get; set; }//邮件主题
            public string EmailBody { get; set; }//邮件正文

            //public string EmailTo { get; set; }//收件人邮箱会单独写，因为收件人是一个集合
        }

3、发送邮件的方法

  /// <summary>
        /// 发送邮件方法 
        /// </summary>
        /// <param name="msc">邮箱实体类</param>
        /// <param name="recipient">收件人集合</param> 
        private static void SendEmail(MailsSendClass msc,string recipient)
        {
            System.Net.Mail.SmtpClient client = new System.Net.Mail.SmtpClient();
            client.Host = msc.EmailHost;
            client.UseDefaultCredentials = false;
            client.DeliveryMethod = System.Net.Mail.SmtpDeliveryMethod.Network;
            client.Credentials = new System.Net.NetworkCredential(msc.EmailFrom, msc.EmailPwd);
            System.Net.Mail.MailMessage Message = new System.Net.Mail.MailMessage();
            Message.From = new System.Net.Mail.MailAddress(msc.EmailFrom, "測試人員");
            Message.To.Add(recipient);
            Message.Subject =msc.EmailTitle;
            Message.Body =msc.EmailBody;
            Message.SubjectEncoding = System.Text.Encoding.UTF8;
            Message.BodyEncoding = System.Text.Encoding.UTF8;
            Message.Priority = System.Net.Mail.MailPriority.High;
            Message.IsBodyHtml = true;
            client.Send(Message);
        }

4、线程池发送邮件的方法

 /// <summary>
        /// 线程池发送邮件  
        /// </summary>
        /// <param name="msc">邮箱实体类</param>
        /// <param name="recipients">收件人集合</param>
        /// <returns></returns>
        private static bool SendEmailsUsingThreadPool(MailsSendClass msc, List<string> recipients)
        {
            try
            {
                //线程数  
                var coreCount = Environment.ProcessorCount;
                //邮件数  
                var itemCount = recipients.Count;
                //每个线程执行记录数  
                var batchSize = itemCount / coreCount;
                var pending = coreCount;
                using (var mre = new ManualResetEvent(false))
                {
                    for (int batchCount = 0; batchCount < coreCount; batchCount++)
                    {
                        var lower = batchCount * batchSize;
                        var upper = (batchCount == coreCount - 1) ? itemCount : lower + batchSize;
                        ThreadPool.QueueUserWorkItem(st =>
                        {
                            for (int i = lower; i < upper; i++)
                                SendEmail(msc,recipients[i]);
                            if (Interlocked.Decrement(ref pending) == 0)
                                mre.Set();
                        });
                    }
                    mre.WaitOne();
                }
                return true;
            }
            catch (Exception exc)
            {
                return false;
            }
        }

5、点击按钮，发送邮件

  protected void btn_SendMail_Click(object sender, EventArgs e)
        {
            MailsSendClass msc = new MailsSendClass();
            msc.EmailHost = "smtp.qq.com";
            msc.EmailFrom = "2535745217@qq.com";
            msc.EmailPwd = "szq7952036";
            msc.EmailTitle = "主题";
            msc.EmailBody = "内容";
            string Shoujr = "3230863302@qq.com;473983390@qq.com;1574875692@qq.com;2963513639@qq.com;";
            string recipient1 = Shoujr.Trim().TrimEnd(';');//去掉最后一个 ';'
            string[] Emaillist = recipient1.Split(';');
            List<string> lists = new List<string>(Emaillist);
            if (SendEmailsUsingThreadPool(msc,lists))
            {
                Response.Write("<script>alert('发送成功')</script>");
            }
            else
            {
                Response.Write("<script>alert('发送失败')</script>");
            }
        }