为什么我的邮件要程序关掉才能发送成功

Question

各位大哥大姐，下面是我用c#写的发送邮件的一个程序，为什么每次发送完，
都要把程序关闭掉才开始发送邮件，谢谢各位指教！！   
  
   private void button1_Click(object sender, EventArgs e)
        {
            //Smpt
            SmtpClient client =
                new SmtpClient("192.168.0.4", 25);
            //送信元
            MailAddress from = new MailAddress("[email protected]");
            //送信先
            MailAddress to = new MailAddress("[email protected]");
            //メッセージ
            MailMessage message = new MailMessage(from ,to);
            //メッセージ本体
            message.Body = "Hello";
            //件名
            message.Subject = "Test message";
            for (int i = 0; i < 2; i++)
            {
                client.Send(message);
 
            }
            message.Dispose();
        }

Answer 1

看我也写了一个来PI美。哈哈哈。
    protected void Button3_Click(object sender, EventArgs e)
    {                  int iRecipient;                                     //收件人个数．
            string[] recipients;                                //收件人EMAIL地址.
            recipients = this.TextBox2.Text.Trim().Split(',');  //获取各收件人.            try
            {
                for (iRecipient = 0; iRecipient < recipients.Length; iRecipient++)
                {                    if (recipients[iRecipient].Trim().Length != 0)
                    {
                        MailMessage mailObj;
                        mailObj = new MailMessage();
                        SmtpMail.SmtpServer = TextBox3.Text.Trim();
                        mailObj.From = TextBox1.Text.Trim();
                        mailObj.To = recipients[iRecipient].Trim();
                        mailObj.Subject = this.TextBox4.Text.Trim();
                        mailObj.BodyFormat = MailFormat.Html;
                        mailObj.Body = this.TextBox5.Text.Trim();
                        if (FileUpload1.PostedFile.ContentLength > 0)
                        {
                            // 创建一个MailAttachment对象来附加一个文件到email。 
                            mailObj.Attachments.Add(new MailAttachment(FileUpload1.PostedFile.FileName));
                        }
                        SmtpMail.Send(mailObj);
                        mailObj = null;
                        Label1.Text = "邮件发送成功";
                        TextBox1.Text = "";
                        TextBox2.Text = "";
                        TextBox4.Text = "";
                        TextBox5.Text = "";
                    }
                }
            }
            catch (Exception exc)
            {
                Label1.Text += "邮件发送失败！原因是：" + exc.Message;
            }    }