c# - 连接尝试失败 HRESULT 异常 : 0x8007274C

Question

我尝试通过网络向 Yahoo 邮件帐户发送邮件，并且在前一天运行良好。今天，当我在没有任何更改的情况下运行相同的代码(但使用不同的网络连接)时，显示以下错误。

A connection attempt failed because the connected party did not properly respond 
after a period of time, or established connection failed because connected host 
has failed to respond. (Exception from HRESULT: 0x8007274C)  

我了解到错误是由于连接超时。我检查了 Allow network loopback 属性，但仍显示错误。
有什么办法可以解决吗？

为什么它运行了一次，现在却不运行了？

使用 System.Threading.Tasks；使用 EASendMailRT；

private async void buttonSend_Click(object sender, RoutedEventArgs e)  
          {
              buttonSend.IsEnabled = false;  
              await Send_Email();  
              buttonSend.IsEnabled = true;  
          }  
          private async Task Send_Email()  
          {
              string Result = "";  
              try  
              {  
              SmtpMail oMail = new SmtpMail("TryIt");  
              SmtpClient oSmtp = new SmtpClient();  

            // Set sender email address, please change it to yours
              oMail.From = new MailAddress("apple@yahoo.com");  

            // Add recipient email address, please change it to yours
            oMail.To.Add(new MailAddress("banana@yahoo.com"));

            // Set email subject and email body text
              oMail.Subject = "Subject entered";
              oMail.TextBody = "body of mail";  

              // Your SMTP server address  
              SmtpServer oServer = new SmtpServer("smtp.mail.yahoo.com");  

              // User and password for SMTP authentication              
              oServer.User = "apple@yahoo.com";    
              oServer.Password = "testpassword";  
              //yahoomail requires TLS/SSL and SMTP port is 465
              // If your SMTP server requires TLS connection on 25 port, please add this line    
              //oServer.ConnectType = SmtpConnectType.ConnectSSLAuto;  

              // If your SMTP server requires SSL connection on 465 port, please add this line  
              oServer.Port = 465;  
              oServer.ConnectType = SmtpConnectType.ConnectSSLAuto;  

              await oSmtp.SendMailAsync(oServer, oMail);  
              Result = "Email was sent";  
          }  
          catch (Exception ep)  
          {
              Result = String.Format("Failed to send email with the following error: {0}", ep.Message);  
          }  

          // Display Result by Diaglog box  
          Windows.UI.Popups.MessageDialog dlg = new  
              Windows.UI.Popups.MessageDialog(Result);  

          await dlg.ShowAsync();  
      }  

Answer 1

我之前遇到过这种情况，当时我的防病毒软件认为未知/未签名的进程正在尝试发送电子邮件。尝试关闭您的 A/V 或防火墙一分钟，然后重试。