SMTP email from C#

       /// <summary>
        /// 一人一附件发送邮件
        ///  2017-05-17 涂聚文  GeovinDu
        /// </summary>
        /// <param name="To">接收邮件人</param>
        /// <param name="Subject">邮件标题</param>
        /// <param name="Msg">邮件内容</param>
        /// <param name="bodyHtml">是否網頁</param>
        /// <param name="AttachmentStream"></param>
        /// <param name="AttachmentFileName">附件</param>
        /// <returns></returns>
        public static bool SendEmaildu(string To, string Subject, string Msg, bool bodyHtml, MemoryStream AttachmentStream,string AttachmentFileName)
        {
            bool SendOk = false;
            try
            {
                System.Net.Mail.MailMessage newMsg = new System.Net.Mail.MailMessage(System.Configuration.ConfigurationManager.AppSettings["mailCfg"], To, Subject, Msg);
                newMsg.BodyEncoding = System.Text.Encoding.UTF8;
                newMsg.HeadersEncoding = System.Text.Encoding.UTF8;
                newMsg.SubjectEncoding = System.Text.Encoding.UTF8;

                System.Net.Mail.SmtpClient smtpClient = new System.Net.Mail.SmtpClient();
                //smtpClient.Credentials = new NetworkCredential("geovindu@dusystem.com","888888");
                //smtpClient.Port = 25;
                //smtpClient.EnableSsl = false;
                if (AttachmentStream != null && AttachmentFileName != null)
                {

                    // ADD AN ATTACHMENT.
                    //String sFile = @"C:\Source\LNS_IS.TXT";
                    //MailAttachment oAttch = new MailAttachment(sFile, MailEncoding.Base64);
                    //string filePath = @"C:\TestEmail\SKYPE11月黑咭生日會員.xls";
                    //MemoryStream memStream = new MemoryStream();
                    //using (FileStream fileStream = File.OpenRead(filePath))
                    //{

                    //    memStream.SetLength(fileStream.Length);
                    //    fileStream.Read(memStream.GetBuffer(), 0, (int)fileStream.Length);
                    //}

                    newMsg.Attachments.Add(new Attachment(AttachmentStream, AttachmentFileName)); //MediaTypeNames.Image.Jpeg)                
                  

                    //System.Net.Mail.Attachment attachment = new System.Net.Mail.Attachment(AttachmentStream, AttachmentFileName);
                    //System.Net.Mime.ContentDisposition disposition = attachment.ContentDisposition;
                    //disposition.FileName = AttachmentFileName;
                    //disposition.DispositionType = System.Net.Mime.DispositionTypeNames.Attachment;
                    //newMsg.Attachments.Add(attachment);

                }
                newMsg.IsBodyHtml = bodyHtml;
               
                smtpClient.Send(newMsg);
                SendOk = true;
                //return SENT_OK;
            }
            catch (Exception ex)
            {
                ex.Message.ToString();
                AttachmentStream.Close();
                SendOk = false;
                //"Error: " + ex.Message + "<br/><br/>Inner Exception: "+ ex.InnerException;

                
            }
            AttachmentStream.Close();
            return SendOk;

        }
        /// <summary>
        /// 一人一附件发送邮件
        /// 2017-05-17 涂聚文  GeovinDu
        /// </summary>
        /// <param name="To">接收邮件人</param>
        /// <param name="Subject">邮件标题</param>
        /// <param name="Msg">邮件内容</param>
        /// <param name="bodyHtml">是否網頁</param>
        /// <param name="AttachmentFileName">附件</param>
        /// <returns></returns>
        public static bool SendEmaildu(string To, string Subject, string Msg, bool bodyHtml, string AttachmentFileName)
        {
            MemoryStream AttachmentStream = new MemoryStream();
            bool SendOk = false;
            try
            {
                System.Net.Mail.MailMessage newMsg = new System.Net.Mail.MailMessage(System.Configuration.ConfigurationManager.AppSettings["mailCfg"], To, Subject, Msg);
                newMsg.BodyEncoding = System.Text.Encoding.UTF8;
                newMsg.HeadersEncoding = System.Text.Encoding.UTF8;
                newMsg.SubjectEncoding = System.Text.Encoding.UTF8;

                System.Net.Mail.SmtpClient smtpClient = new System.Net.Mail.SmtpClient();
                //smtpClient.Credentials = new NetworkCredential("geovindu@dusystem.com","888888");
                //smtpClient.Port = 25;
                //smtpClient.EnableSsl = false;
                if (AttachmentStream != null && AttachmentFileName != null)
                {

                    // ADD AN ATTACHMENT.
                    //String sFile = @"C:\Source\LNS_IS.TXT";
                    //MailAttachment oAttch = new MailAttachment(sFile, MailEncoding.Base64);
                    //string filePath = @"C:\TestEmail\SKYPE11月黑咭生日會員.xls";
                    //MemoryStream memStream = new MemoryStream();
                    //using (FileStream fileStream = File.OpenRead(filePath))
                    //{

                    //    memStream.SetLength(fileStream.Length);
                    //    fileStream.Read(memStream.GetBuffer(), 0, (int)fileStream.Length);
                    //}

                    newMsg.Attachments.Add(new Attachment(AttachmentStream, AttachmentFileName)); //MediaTypeNames.Image.Jpeg)                


                    //System.Net.Mail.Attachment attachment = new System.Net.Mail.Attachment(AttachmentStream, AttachmentFileName);
                    //System.Net.Mime.ContentDisposition disposition = attachment.ContentDisposition;
                    //disposition.FileName = AttachmentFileName;
                    //disposition.DispositionType = System.Net.Mime.DispositionTypeNames.Attachment;
                    //newMsg.Attachments.Add(attachment);

                }
                newMsg.IsBodyHtml = bodyHtml;                
                smtpClient.Send(newMsg);
                SendOk = true;
                //return SENT_OK;
            }
            catch (Exception ex)
            {
                ex.Message.ToString();
                AttachmentStream.Close();
                SendOk = false;
                //"Error: " + ex.Message + "<br/><br/>Inner Exception: "+ ex.InnerException;


            }
            AttachmentStream.Close();
            return SendOk;

        }

        /// <summary>
        /// 一人多附件发送邮件
        /// 2019-06-18 涂聚文 GeovinDu
        /// </summary>
        /// <param name="To">接收邮件人</param>
        /// <param name="Subject">邮件标题</param>
        /// <param name="Msg">邮件内容</param>
        /// <param name="bodyHtml">是否網頁</param>
        /// <param name="AttachmentFiles">多附件</param>
        /// <returns></returns>
        public static bool SendEmailduFiles(string To, string Subject, string Msg, bool bodyHtml, List<string> AttachmentFiles)
        {
            MemoryStream AttachmentStream = new MemoryStream();
            bool SendOk = false;
            try
            {
                System.Net.Mail.MailMessage newMsg = new System.Net.Mail.MailMessage(System.Configuration.ConfigurationManager.AppSettings["mailCfg"], To, Subject, Msg);
                newMsg.BodyEncoding = System.Text.Encoding.UTF8;
                newMsg.HeadersEncoding = System.Text.Encoding.UTF8;
                newMsg.SubjectEncoding = System.Text.Encoding.UTF8;

                System.Net.Mail.SmtpClient smtpClient = new System.Net.Mail.SmtpClient();
                //smtpClient.Credentials = new NetworkCredential("geovindu@dusystem.com","888888");
                //smtpClient.Port = 25;
                //smtpClient.EnableSsl = false;
               


                if (AttachmentStream != null && AttachmentFiles != null)
                {
 
                 
                    foreach (string filename in AttachmentFiles)
                    {
                        newMsg.Attachments.Add(new Attachment(AttachmentStream, filename)); //MediaTypeNames.Image.Jpeg)   
                       
                    }     

                }
                newMsg.IsBodyHtml = bodyHtml;               
                smtpClient.Send(newMsg);
                SendOk = true;
            }
            catch (Exception ex)
            {
                ex.Message.ToString();
                AttachmentStream.Close();
                SendOk = false;
            }
            AttachmentStream.Close();
            return SendOk;
        }

        /// <summary>
        /// 多人多附件发送邮件
        /// 不考虑统计每封邮件发送状态（另外考虑完善代码）
        ///  2019-06-18 涂聚文 GeovinDu
        /// </summary>
        /// <param name="Tos">多人接收邮件人</param>
        /// <param name="Subject">邮件标题</param>
        /// <param name="Msg">邮件内容</param>
        /// <param name="bodyHtml">是否網頁</param>
        /// <param name="AttachmentFiles">多附件</param>
        /// <returns></returns>
        public static bool SendEmailsAndFiles(List<string> Tos, string Subject, string Msg, bool bodyHtml, List<string> AttachmentFiles)
        {
            MemoryStream AttachmentStream = new MemoryStream();
            bool SendOk = false;
            List<Attachment> all = new List<Attachment>();
            try
            {
                if (AttachmentStream != null && AttachmentFiles != null)
                {
                    foreach (string filename in AttachmentFiles)
                    {

                        all.Add(new Attachment(AttachmentStream, filename));
                    }
                }
                if (Tos.Count > 0)
                {


                    foreach (string To in Tos)
                    {
                        System.Net.Mail.MailMessage newMsg = new System.Net.Mail.MailMessage(System.Configuration.ConfigurationManager.AppSettings["mailCfg"], To, Subject, Msg);
                        newMsg.BodyEncoding = System.Text.Encoding.UTF8;
                        newMsg.HeadersEncoding = System.Text.Encoding.UTF8;
                        newMsg.SubjectEncoding = System.Text.Encoding.UTF8;
                        System.Net.Mail.SmtpClient smtpClient = new System.Net.Mail.SmtpClient();
                        //smtpClient.Credentials = new NetworkCredential("geovindu@dusystem.com","888888");
                        //smtpClient.Port = 25;
                        //smtpClient.EnableSsl = false;
                        if (AttachmentStream != null && AttachmentFiles != null)
                        {
                            foreach (Attachment attname in all)
                            {
                                newMsg.Attachments.Add(attname); //MediaTypeNames.Image.Jpeg)   

                            }
                        }
                        newMsg.IsBodyHtml = bodyHtml;                        
                        smtpClient.Send(newMsg);
                        SendOk = true;
                   }
                }
            }
            catch (Exception ex)
            {
                ex.Message.ToString();
                AttachmentStream.Close();
                SendOk = false;
            }
            AttachmentStream.Close();
            return SendOk;
        }

　　测试代码：

            MemoryStream theMemStream = new MemoryStream();
            string file = @"C:\TestEmail\SKYPE11月黑咭生日會員.xls";  //C:\TestEmail\Top1000WorldBanks2014.pdf
            if (File.Exists(file))
            {
                //AttachmentStream = File.Open(file, FileMode.Open, FileAccess.Read);


                byte[] filebyte = MirosoftSmptHelper.ReadFile(file);

                theMemStream.Write(filebyte, 0, filebyte.Length);// = File.OpenRead(file); 
                theMemStream.Position = 0;

                //theMemStream.Close();

                // AttachmentStream = theMemStream;// BytesToStream(filebyte); //new MemoryStream(filebyte);// // BytesToStream(filebyte);// FileToStream(file);// 

                //AttachmentStream.CanTimeout =true;
                //AttachmentStream.ReadTimeout = 1000;
                //AttachmentStream.WriteTimeout = 1000;
                //AttachmentStream = BytesToStream(filebyte);

                //theMemStream.Close();
            }
            List<string> AttachmentFiles = new List<string>();
            AttachmentFiles.Add("馬拉松獎牌刻字.xlsx");
            AttachmentFiles.Add("进一步优化供给推动消费平稳增长2019.pdf");
            AttachmentFiles.Add("逃犯条例草案.pdf");
            AttachmentFiles.Add("复习卷14.doc");
            List<string> Tos = new List<string>();
            Tos.Add("geovindu@163.com");
            Tos.Add("geovindu@hotmail.com");
            Tos.Add("geovi@qq.com");

            //1.一人一附件
            //bool issend = MirosoftSmptHelper.SendEmaildu("geovindu@163.com", "中文文件名.net 4.0,geovindu 涂聚文塗聚文工團、", "<p> 生命運浪漫滿屋geovindu江蘇黃河</p><br/><p>上官放個屁，下官一台戲</p>", true,"馬拉松獎牌刻字.xlsx");
            //2.一人多附件
            //bool issend = MirosoftSmptHelper.SendEmailduFiles("geovindu@163.com", "中文文件名.net 4.0,geovindu 涂聚文塗聚文工團、", "<p> 生命運浪漫滿屋geovindu江蘇黃河</p><br/><p>上官放個屁，下官一台戲</p>", true, AttachmentFiles);
           //3.多人多附件
            bool issend = MirosoftSmptHelper.SendEmailsAndFiles(Tos, "中文文件名.net 4.0,geovindu 涂聚文塗聚文工團、", "<p> 生命運浪漫滿屋geovindu江蘇黃河</p><br/><p>上官放個屁，下官一台戲</p>", true, AttachmentFiles);
            theMemStream.Close();
            if (issend)
            {
                MessageBox.Show("ok");
            }
            else
            {
                MessageBox.Show("no");
            }
        }

　　不忘初心，方得始终；初心易得，始终难守。

 

        /// <summary>
        /// 多人多附件发送邮件
        /// 不考虑统计每封邮件发送状态（另外考虑完善代码）
        ///  2019-06-18 涂聚文 GeovinDu
        ///  2019-07-01
        /// </summary>
        /// <param name="Tos">多人接收邮件人</param>
        /// <param name="Subject">邮件标题</param>
        /// <param name="Msg">邮件内容</param>
        /// <param name="bodyHtml">是否網頁</param>
        /// <param name="AttachmentFiles">多附件--具体文件地址</param>
        /// <returns></returns>
        public static bool SendEmailsAndFiles(List<string> Tos, string Subject, string Msg, bool bodyHtml, List<string> AttachmentFiles)
        {
            MemoryStream AttachmentStream = new MemoryStream();
            bool SendOk = false;
            List<Attachment> all = new List<Attachment>();
            try
            {
                if (AttachmentStream != null && AttachmentFiles != null)
                {
                    foreach (string filename in AttachmentFiles)
                    {
                        Attachment attachment = new Attachment(filename, MediaTypeNames.Application.Octet); // //AttachmentStream, filename
                        ContentDisposition disposition = attachment.ContentDisposition;
                        disposition.CreationDate = File.GetCreationTime(filename);
                        disposition.ModificationDate = File.GetLastWriteTime(filename);
                        disposition.ReadDate = File.GetLastAccessTime(filename);
                        disposition.FileName = Path.GetFileName(filename);
                        disposition.Size = new FileInfo(filename).Length;                      
                        disposition.DispositionType = DispositionTypeNames.Attachment;
                        all.Add(attachment); //new Attachment(AttachmentStream, filename)
                    }
                }
                if (Tos.Count > 0)
                {


                    foreach (string To in Tos)
                    {
                        System.Net.Mail.MailMessage newMsg = new System.Net.Mail.MailMessage(System.Configuration.ConfigurationManager.AppSettings["mailCfg"], To, Subject, Msg);
                        newMsg.BodyEncoding = System.Text.Encoding.UTF8;
                        newMsg.HeadersEncoding = System.Text.Encoding.UTF8;
                        newMsg.SubjectEncoding = System.Text.Encoding.UTF8;
                        System.Net.Mail.SmtpClient smtpClient = new System.Net.Mail.SmtpClient();
                        //smtpClient.Credentials = new NetworkCredential("geovindu@dusystem.com","888888");
                        //smtpClient.Port = 25;
                        //smtpClient.EnableSsl = false;
                        if (AttachmentStream != null && AttachmentFiles != null)
                        {
                            foreach (Attachment attname in all)
                            {

                                
                                newMsg.Attachments.Add(attname); //MediaTypeNames.Image.Jpeg)   

                            }
                        }
                        newMsg.IsBodyHtml = bodyHtml;                        
                        smtpClient.Send(newMsg);
                        SendOk = true;
                   }
                }
            }
            catch (Exception ex)
            {
                ex.Message.ToString();
                AttachmentStream.Close();
                SendOk = false;
            }
            AttachmentStream.Close();
            return SendOk;
        }

        /// <summary>
        /// 多人多附件发送邮件
        /// 不考虑统计每封邮件发送状态（另外考虑完善代码）
        ///  2019-07-01 涂聚文 GeovinDu
        /// </summary>
        /// <param name="Tos">多人接收邮件人</param>
        /// <param name="Subject">邮件标题</param>
        /// <param name="Msg">邮件内容</param>
        /// <param name="bodyHtml">是否網頁</param>
        /// <param name="AttachmentFiles">多附件--根据运行程序目录地址</param>
        /// <returns></returns>
        public static bool SendEmailsAndLocalFiles(List<string> Tos, string Subject, string Msg, bool bodyHtml, List<string> AttachmentFiles)
        {
            MemoryStream AttachmentStream = new MemoryStream();
            bool SendOk = false;
            List<Attachment> all = new List<Attachment>();
            try
            {
                if (AttachmentStream != null && AttachmentFiles != null)
                {
                    foreach (string filename in AttachmentFiles)
                    {
                        //具体的文件地址，用此法
                        //Attachment attachment = new Attachment(filename, MediaTypeNames.Application.Octet); // //AttachmentStream, filename
                        //ContentDisposition disposition = attachment.ContentDisposition;
                        //disposition.CreationDate = File.GetCreationTime(filename);
                        //disposition.ModificationDate = File.GetLastWriteTime(filename);
                        //disposition.ReadDate = File.GetLastAccessTime(filename);
                        //disposition.FileName = Path.GetFileName(filename);
                        //disposition.Size = new FileInfo(filename).Length;
                        //disposition.DispositionType = DispositionTypeNames.Attachment;
                        all.Add(new Attachment(AttachmentStream, filename));//在运行程序的目录的文件没有问题，可执行。如是不是此语言件地址，附件无效
                    }
                }
                if (Tos.Count > 0)
                {


                    foreach (string To in Tos)
                    {
                        System.Net.Mail.MailMessage newMsg = new System.Net.Mail.MailMessage(System.Configuration.ConfigurationManager.AppSettings["mailCfg"], To, Subject, Msg);
                        newMsg.BodyEncoding = System.Text.Encoding.UTF8;
                        newMsg.HeadersEncoding = System.Text.Encoding.UTF8;
                        newMsg.SubjectEncoding = System.Text.Encoding.UTF8;
                        System.Net.Mail.SmtpClient smtpClient = new System.Net.Mail.SmtpClient();
                        //smtpClient.Credentials = new NetworkCredential("geovindu@dusystem.com","888888");
                        //smtpClient.Port = 25;
                        //smtpClient.EnableSsl = false;
                        if (AttachmentStream != null && AttachmentFiles != null)
                        {
                            foreach (Attachment attname in all)
                            {
                                newMsg.Attachments.Add(attname); //MediaTypeNames.Image.Jpeg)   

                            }
                        }
                        newMsg.IsBodyHtml = bodyHtml;
                        smtpClient.Send(newMsg);
                        SendOk = true;
                    }
                }
            }
            catch (Exception ex)
            {
                ex.Message.ToString();
                AttachmentStream.Close();
                SendOk = false;
            }
            AttachmentStream.Close();
            return SendOk;
        }

　　

      /// <summary>
        /// 20190702 多人邮件
        /// geovindu 涂聚文
        /// </summary>
        /// <param name="Mails"></param>
        /// <param name="Subject"></param>
        /// <param name="Msg"></param>
        /// <param name="bodyHtml"></param>
        /// <param name="AttachmentFiles"></param>
        /// <returns></returns>
        public static bool SendEmailsFiles(List<MailAddress> Mails, string Subject, string Msg, bool bodyHtml, List<string> AttachmentFiles)
        {
            MemoryStream AttachmentStream = new MemoryStream();
            bool SendOk = false;
            List<Attachment> all = new List<Attachment>();
            try
            {
                if (AttachmentStream != null && AttachmentFiles != null)
                {
                    foreach (string filename in AttachmentFiles)
                    {
                        //具体的文件地址，用此法
                        Attachment attachment = new Attachment(filename, MediaTypeNames.Application.Octet); // //AttachmentStream, filename
                        ContentDisposition disposition = attachment.ContentDisposition;
                        disposition.CreationDate = File.GetCreationTime(filename);
                        disposition.ModificationDate = File.GetLastWriteTime(filename);
                        disposition.ReadDate = File.GetLastAccessTime(filename);
                        disposition.FileName = Path.GetFileName(filename);
                        disposition.Size = new FileInfo(filename).Length;
                        disposition.DispositionType = DispositionTypeNames.Attachment;
                        all.Add(attachment);//在运行程序的目录的文件没有问题，可执行。如是不是此语言件地址，附件无效
                    }
                }
                if (Mails.Count > 0)
                {

                    int c = 1;
                    foreach (MailAddress ToAddress in Mails)
                    {

                        MailAddress from=new MailAddress(System.Configuration.ConfigurationManager.AppSettings["mailCfg"],System.Configuration.ConfigurationManager.AppSettings["displayName"]);
                        //from.DisplayName="";
                       // from.Address=;
                        System.Net.Mail.MailMessage newMsg = new System.Net.Mail.MailMessage();
                        newMsg.From = from;
                        newMsg.To.Add(ToAddress);
                        newMsg.Subject = Subject;
                        newMsg.Body = Msg;
                        newMsg.BodyEncoding = System.Text.Encoding.UTF8;
                        newMsg.HeadersEncoding = System.Text.Encoding.UTF8;
                        newMsg.SubjectEncoding = System.Text.Encoding.UTF8;
                        System.Net.Mail.SmtpClient smtpClient = new System.Net.Mail.SmtpClient();
                        //smtpClient.Credentials = new NetworkCredential("geovindu@dusystem.com","888888");
                        //smtpClient.Port = 25;
                        //smtpClient.EnableSsl = false;
                        if (AttachmentStream != null && AttachmentFiles != null)
                        {
                            foreach (Attachment attname in all)
                            {
                                newMsg.Attachments.Add(attname); //MediaTypeNames.Image.Jpeg)  
                            }
                        }
                        newMsg.IsBodyHtml = bodyHtml;
                        //smtpClient.Send(newMsg);
                        smtpClient.SendCompleted += new SendCompletedEventHandler(SendCompletedCallback);
                        string userState = "test message:"+c.ToString();
                        smtpClient.SendAsync(newMsg, userState);
                        SendOk = true;
                        c++;
                    }
                    
                }
            }
            catch (Exception ex)
            {
                ex.Message.ToString();
                AttachmentStream.Close();
                SendOk = false;
            }
            AttachmentStream.Close();
            return SendOk;
        }
        /// <summary>
        /// 一人多附件
        /// </summary>
        /// <param name="Mails"></param>
        /// <param name="Subject"></param>
        /// <param name="Msg"></param>
        /// <param name="bodyHtml"></param>
        /// <param name="AttachmentFiles"></param>
        /// <returns></returns>
        public static bool SendEmailFiles(MailAddress Mails, string Subject, string Msg, bool bodyHtml, List<string> AttachmentFiles)
        {
            MemoryStream AttachmentStream = new MemoryStream();
            bool SendOk = false;
            List<Attachment> all = new List<Attachment>();
            try
            {
                if (AttachmentStream != null && AttachmentFiles != null)
                {
                    foreach (string filename in AttachmentFiles)
                    {
                        //具体的文件地址，用此法
                        Attachment attachment = new Attachment(filename, MediaTypeNames.Application.Octet); // //AttachmentStream, filename
                        ContentDisposition disposition = attachment.ContentDisposition;
                        disposition.CreationDate = File.GetCreationTime(filename);
                        disposition.ModificationDate = File.GetLastWriteTime(filename);
                        disposition.ReadDate = File.GetLastAccessTime(filename);
                        disposition.FileName = Path.GetFileName(filename);
                        disposition.Size = new FileInfo(filename).Length;
                        disposition.DispositionType = DispositionTypeNames.Attachment;
                        all.Add(attachment);//在运行程序的目录的文件没有问题，可执行。如是不是此语言件地址，附件无效
                    }
                } 
   

                    MailAddress from = new MailAddress(System.Configuration.ConfigurationManager.AppSettings["mailCfg"], System.Configuration.ConfigurationManager.AppSettings["displayName"]);
                    //from.DisplayName="";
                    // from.Address=;
                    System.Net.Mail.MailMessage newMsg = new System.Net.Mail.MailMessage();
                    newMsg.From = from;
                    newMsg.To.Add(Mails);
                    newMsg.Subject = Subject;
                    newMsg.Body = Msg;
                    newMsg.BodyEncoding = System.Text.Encoding.UTF8;
                    newMsg.HeadersEncoding = System.Text.Encoding.UTF8;
                    newMsg.SubjectEncoding = System.Text.Encoding.UTF8;
                    System.Net.Mail.SmtpClient smtpClient = new System.Net.Mail.SmtpClient();
                    //smtpClient.Credentials = new NetworkCredential("geovindu@dusystem.com","888888");
                    //smtpClient.Port = 25;
                    //smtpClient.EnableSsl = false;
                    if (AttachmentStream != null && AttachmentFiles != null)
                    {
                        foreach (Attachment attname in all)
                        {
                            newMsg.Attachments.Add(attname); //MediaTypeNames.Image.Jpeg)  
                        }
                    }
                    newMsg.IsBodyHtml = bodyHtml;
                    //smtpClient.Send(newMsg);
                    smtpClient.SendCompleted += new SendCompletedEventHandler(SendCompletedCallback);
                    string userState = "test message:发送中";
                    smtpClient.SendAsync(newMsg, userState);
                    SendOk = true;                       
                   
                
            }
            catch (Exception ex)
            {
                ex.Message.ToString();
                AttachmentStream.Close();
                SendOk = false;
            }
            AttachmentStream.Close();
            return SendOk;
        }

　　测试

  List<MailAddress> mails = new List<MailAddress>();
            MailAddress address = null;
            address = new MailAddress("geovindu@163.com", "涂聚文", Encoding.UTF8);           
            mails.Add(address);
            address = new MailAddress("geovindu@hotmail.com", "塗聚文", Encoding.UTF8);
            mails.Add(address);
            address = new MailAddress("463588883@qq.com", "捷為工作室", Encoding.UTF8);
            mails.Add(address);
            string strMessage = string.Empty;
            string subject = string.Empty;

            subject=txtSubject.Text.Trim();
            strMessage = htmlEditUserControl1.HtmlEditControl.DocumentText;

            //1.一人一附件
            //bool issend = MirosoftSmptHelper.SendEmaildu("geovindu@163.com", "中文文件名.net 4.0,geovindu 涂聚文塗聚文工團、", "<p> 生命運浪漫滿屋geovindu江蘇黃河</p><br/><p>上官放個屁，下官一台戲</p>", true,"馬拉松獎牌刻字.xlsx");
            //2.一人多附件
            //bool issend = MirosoftSmptHelper.SendEmailduFiles("geovindu@163.com", "中文文件名.net 4.0,geovindu 涂聚文塗聚文工團、", "<p> 生命運浪漫滿屋geovindu江蘇黃河</p><br/><p>上官放個屁，下官一台戲</p>", true, AttachmentFiles);
           //3.多人多附件
            //bool issend = MirosoftSmptHelper.SendEmailsAndFiles(Tos, subject, strMessage, true, AttachmentFiles);
            bool issend = MirosoftSmptHelper.SendEmailsFiles(mails, subject, strMessage, true, AttachmentFiles);