Send Email with Multiple Threads(Mass Mail) in C#¶

using System;
using System.Collections.Generic;
using System.Text;
using EASendMail; //add EASendMail namespace

namespace mysendemail
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] arRcpt = new string[]{"test1@adminsystem.com",
                "test2@adminsystem.com",
                "test3@adminsystem.com" };

            int nRcpt = arRcpt.Length;
            SmtpMail[] arMail = new SmtpMail[nRcpt];
            SmtpClient[] arSmtp = new SmtpClient[nRcpt];
            SmtpClientAsyncResult[] arResult = new SmtpClientAsyncResult[nRcpt];

            for (int i = 0; i < nRcpt; i++)
            {
                arMail[i] = new SmtpMail("TryIt");
                arSmtp[i] = new SmtpClient();
            }

            for (int i = 0; i < nRcpt; i++)
            {
                SmtpMail oMail = arMail[i];
                // Set sender email address
                oMail.From = "sender@emailarchitect.net";
                // Set recipient email address
                oMail.To = arRcpt[i];

                // Set email subject
                oMail.Subject = "mass email test from c#";
                // Set email body
                oMail.TextBody = "test from c#, this email is sent to " + arRcpt[i];

                // Your smtp server address
                SmtpServer oServer = new SmtpServer("smtp.emailarchitect.net");

                // User and password for ESMTP authentication
                oServer.User = "test@emailarchitect.net";
                oServer.Password = "testpassword";

                // Most mordern SMTP servers require SSL/TLS connection now.
                // ConnectTryTLS means if server supports SSL/TLS, SSL/TLS will be used automatically.
                oServer.ConnectType = SmtpConnectType.ConnectTryTLS;

                // If your SMTP server uses 587 port
                // oServer.Port = 587;

                // If your SMTP server requires SSL/TLS connection on 25/587/465 port
                // oServer.Port = 25; // 25 or 587 or 465
                // oServer.ConnectType = SmtpConnectType.ConnectSSLAuto;

                SmtpClient oSmtp = arSmtp[i];

                // Submit email to BeginSendMail method and return
                // to process another email
                arResult[i] = oSmtp.BeginSendMail(oServer, oMail, null, null);
                Console.WriteLine(String.Format("Start to send email to {0} ...",
                    arRcpt[i] ));
            }

            // All emails were sent by BeginSendMail Method
            // now get result by EndSendMail method
            int nSent = 0;
            while (nSent < nRcpt)
            {
                for (int i = 0; i < nRcpt; i++)
                {
                    // this email has been sent
                    if (arResult[i] == null)
                        continue;
                    // wait for specified email ...
                    if (!arResult[i].AsyncWaitHandle.WaitOne(10, false))
                    {
                        continue;
                    }
                    try
                    {
                        // this email is finished, using EndSendMail to get result
                        arSmtp[i].EndSendMail(arResult[i]);
                        Console.WriteLine(String.Format("Send email to {0} successfully",
                            arRcpt[i]));
                    }
                    catch (Exception ep)
                    {
                        Console.WriteLine(
                           String.Format("Failed to send email to {0} with error {1}: ",
                           arRcpt[i], ep.Message));
                    }
                    // Set this email result to null, then it won't be processed again
                    arResult[i] = null;
                    nSent++;
                }
            }
        }
    }
}