交易失败。服务器响应为：IRFRPAR-C690-06-D2-incoming.host.com

Question

我正在尝试使用窗口凭据发送电子邮件。以下是我的代码：-

            string to = "abc@host.com";
            string from = "def@host.com";
            MailMessage message = new MailMessage(from, to);
            message.Subject = "Using the new SMTP client.";
            message.Body = @"Using this new feature, you can send an email message from an application very easily.";
            SmtpClient client = new SmtpClient("smtp.host.com");
      
            client.UseDefaultCredentials = true;
            

            try
            {
                client.Send(message);
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.ToString());
            }

然后我收到此错误交易失败。服务器响应为：IRFRPAR-C690-06-D2-incoming.host.com