當我運行代碼，併發送它顯示發送失敗

Question

嗨，大家好，我有問題發送羣發郵件使用Windows窗體中的列表框......它顯示發送失敗，當我嘗試發送大宗郵件..這裏是我的代碼我不知道我檢查和檢查的代碼有什麼問題

void SendMail1(string from,string to,string subject,string message,string host,int port,string un,string pw) 
    { 
     MailMessage tm = new MailMessage(); 
     tm.From = new MailAddress(from); 
     tm.To.Add(new MailAddress(to)); 
     tm.Subject = subject; 
     tm.Body = message; 
     tm.IsBodyHtml = true; 
     tm.Priority = MailPriority.Normal; 
     tm.SubjectEncoding = Encoding.UTF8; 
     var smtp = new SmtpClient(); 
     { 
      smtp.Host = host; 
      smtp.Port = port; 
      smtp.EnableSsl = true; 
      smtp.UseDefaultCredentials = true; 
      smtp.DeliveryMethod = SmtpDeliveryMethod.Network;    
      //default credentials 
      smtp.Credentials = new NetworkCredential(un,pw); 
     } 
     smtp.Send(tm); 
     MetroFramework.MetroMessageBox.Show(this, "Bulk Mail Successfully Sent.....", "Success", MessageBoxButtons.OK, MessageBoxIcon.Information); 
    } 


    private void btnSendEmail2_Click(object sender, EventArgs e) 
    { 
     try 
     { 
      if (string.IsNullOrEmpty(txtSubject2.Text) || string.IsNullOrEmpty(txtMessage2.Text) || string.IsNullOrEmpty(txtFrom2.Text) || string.IsNullOrEmpty(txtEmailAddress2.Text) || string.IsNullOrEmpty(txtPassword2.Text) || string.IsNullOrEmpty(txtAttachment2.Text)) 
      { 
       MetroFramework.MetroMessageBox.Show(this, "One Or More Fields Empty..Please Check To See Which Fields Are Empty,Before Sending Mails...", "Warning", MessageBoxButtons.OK, MessageBoxIcon.Warning); 
      } 
      else 
      { 
       //send mails here 
       foreach(string i in lstEmails.Items) 
       { 
        if (i.Trim() != string.Empty) 
        { 
         //declare all fields 
         DataTable dt = new DataTable("tblEmails"); 
         dt.Columns.Add("Email", typeof(string)); 
         dt.Rows.Add(i.ToString()); 
         string _from = txtFrom2.Text.Trim(); 
         string _subject = txtSubject2.Text.Trim(); 
         string _message = txtMessage2.Text.Trim(); 
         string _host = Convert.ToString(ddlProvider2.SelectedItem); 
         int _port = 587; 
         string _un = txtEmailAddress2.Text.Trim(); 
         string _pw = txtPassword2.Text.Trim(); 
         Parallel.ForEach(dt.AsEnumerable(), x => 
         { 
          SendMail1(_from, x["Email"].ToString(), _subject,_message 
           , _host, _port, _un, _pw); 
         }); 

         // MetroFramework.MetroMessageBox.Show(this, i + "\n", "Success", MessageBoxButtons.OK, MessageBoxIcon.Information); 
        } 
        else 
        { 
         MetroFramework.MetroMessageBox.Show(this, "Please Load Some Emails To Send Mail Message...", "Warning", MessageBoxButtons.OK, MessageBoxIcon.Warning); 
        } 
       } 
      } 
     } 
     catch (Exception ex) 
     { 
      MessageBox.Show(ex.Message, "Error", MessageBoxButtons.OK); 
     } 
    } 

Answer 1

您試圖發送電子郵件批量。如果「有時」有效，那麼如果您的發送速率高於管理員設置的閾值，SMTP服務器很可能會拒絕您的消息。如果情況確實如此，您可以做的事情不多，除非管理員將更改其政策以適應您的應用程序。或者，您需要一個不同的SMTP服務（亞馬遜有一個，僅用於像您這樣的批量郵件應用程序）。