Why does sending an email take so long?

using System;
using System.Collect开发者_StackOverflow中文版ions.Generic;
using System.Text;
using System.Diagnostics;
using System.IO;
using System.Net;
using System.Net.Mail;
using System.Threading;

namespace MGR_Backuper
{
    class Program
    {
        static void Main(string[] args)
        {
            string file = "D:\\Programy\\WinRAR\\rar.exe";
            string command = "C:\\Users\\Pawel\\Desktop\\Praca magisterska back\\mgrback-%YEAR%-%MONTH%-%DAY%-%HOUR%-%MINUTES%-%SECONDS%.rar";
            string arg = "a \"%FILENAME%\" \"C:\\Users\\Pawel\\Desktop\\Praca magisterska\\*\" -m5 -ep1 -hppasspass -rr5 -inul -r0";
            var t1 = DateTime.Now;
            command = command.Replace("%YEAR%", "" + t1.Year);
            if (t1.Month < 10) command = command.Replace("%MONTH%", "0" + t1.Month);
            else command = command.Replace("%MONTH%", "" + t1.Month);

            if (t1.Day < 10) command = command.Replace("%DAY%", "0" + t1.Day);
            else command = command.Replace("%DAY%", "" + t1.Day);

            if (t1.Hour < 10) command = command.Replace("%HOUR%", "0" + t1.Hour);
            else command = command.Replace("%HOUR%", "" + t1.Hour);

            if (t1.Minute < 10) command = command.Replace("%MINUTES%", "0" + t1.Minute);
            else command = command.Replace("%MINUTES%", "" + t1.Minute);

            if (t1.Second < 10) command = command.Replace("%SECONDS%", "0" + t1.Second);
            else command = command.Replace("%SECONDS%", "" + t1.Second);

            arg = arg.Replace("%FILENAME%", command);
            var t2 = DateTime.Now;
            Process proc = new System.Diagnostics.Process();
            proc.EnableRaisingEvents = false;
            proc.StartInfo.FileName = file;
            proc.StartInfo.Arguments = arg;

                proc.Start();

                while (!proc.HasExited)
                    Thread.Sleep(50);


            var t3 = DateTime.Now;
            try
            {
                MailMessage mailMsg = new MailMessage();
                mailMsg.To.Add("email@email.com");

                // From
                MailAddress mailAddress = new MailAddress("email@email.com", "Sender");
                mailMsg.From = mailAddress;

                // Subject and Body
                mailMsg.Subject = "MGR";
                mailMsg.Body = "Backup magisterki";
             mailMsg.Attachments.Add(new Attachment(command));

                SmtpClient smtpClient = new SmtpClient("server.serv.com", 587);
                NetworkCredential credentials = new NetworkCredential("login", "password");
                smtpClient.Credentials = credentials;
                smtpClient.Timeout = Int32.MaxValue;
                smtpClient.Send(mailMsg);
            }
            catch (Exception ex)
            { Console.WriteLine(ex.ToString()+"\n"); }
            var t4 = DateTime.Now;
            Console.WriteLine("Czas kompresji: \t{0:0.00}s", (t3 - t2).TotalSeconds);
            Console.WriteLine("Czas wysyłania: \t{0:0.00}s", (t4 - t3).TotalSeconds);
            Console.WriteLine("Czas całkowity: \t{0:0.00}s", (t4 - t1).TotalSeconds);
            Console.ReadKey(true);
        }
    }
}

This is a simple program for backing up some data important to me by sending it to my email address. The created archive is around 1.5 MB. Sending email takes about 7-8 minutes. This is not because of bad connection because when I try to send the same file by email program or webmail it takes 5-6 seconds. Why is sending email this way is so slow?

EDIT :

I made another test

            var ts1 = DateTime.Now;
            smtpClient.Send(mailMsg);
            var ts2 = DateTime.Now;

and it confirmed that smtpClient.Send(mailMsg); is responsible for slowing. Any idea why?

I faced the same problem, It seems that the SMTP server is doing some kind of checking before sending the mail.

I Solved my problem by sending the mail in async way using a new thread as shown below.

private void SendMail(string from, string to)
{
    //your logic to send the mail
}

to send the mail in async way.

ThreadStart threadStart = delegate() { SendMail(from, to); };
Thread thread = new Thread(threadStart);
thread.Start();