title: how to protect classify sent emails as spam in asp.net
body: <blockquote>
    <p><strong>Possible Duplicate:</strong><br>
    <a href="https://stackoverflow.com/questions/1860937/how-can-i-lower-the-spam-score-of-my-email-message">How can I lower the spam score of my email message?</a>  </p>
  </blockquote>
  
  
  
  <p>I have this c# code that can send lots of emails to people . but emails that I sent has classified as spam .what should I do .is there any change that I should apply to my code?I try to get email addresses from sql server data base .and My code can attach one file .</p>
  
  <pre><code>Entities context = new Entities();
  var query = from c in context.Emails select c.EmailAddress;
  MailMessage mail = new MailMessage();
  Regex sample = new Regex(@"^[-!#$%&amp;'*+/0-9=?A-Z^_a-z{|}~](\.?[-!#$%&amp;'*+/0-9=?A-Z^_a-z{|}~])*
                                    @[a-zA-Z](-?[a-zA-Z0-9])*(\.[a-zA-Z](-?[a-zA-Z0-9])*)+$");
  int total = 0;//number of all emails
  int count = 0;//counter for putting interrupt between each 10 sending
  int failed = 0;//number of failed sending
  int success = 0;//number of successful sending
  
  double totalsize = 0;//size of attachment file
  
  if (FileUpload1.HasFile)
  {
      mail.Attachments.Add(new Attachment(FileUpload1.PostedFile.InputStream, FileUpload1.FileName));
      foreach (Attachment attachment in mail.Attachments)
      {
          string size =attachment.ContentStream.Length.ToString ();
          totalsize=Convert .ToDouble (size);
      }
   }
  foreach (var c in query)
  {
      if (count == 10)
      {
          Thread.Sleep(10000);
          count = 0;
      }
      mail.From = new MailAddress("hadi@myhost.com");
      mail.Bcc.Add(new MailAddress(c.ToString()));
      mail.Subject = "hello";
      mail.IsBodyHtml = true;
  
      mail.Body = FCKeditor1.Value.ToString();
  
      SmtpClient smtp = new SmtpClient();
      smtp.Host = "localhost";
      smtp.Port = 25; 
      if ((sample.IsMatch(c.ToString())) &amp;&amp; (sample .IsMatch (mail .From .ToString ())) &amp;&amp; (totalsize&lt;1000000))
      {
        try
          {
              smtp.Send(mail);
              //Response.Write("email has sent to " + c.ToString());
              success++;
  
          }
          catch 
          {
              //Response.Write("email has not sent to " + c.ToString());
              failed++;
          }
          count++;
      }
      total++;
  } 
  </code></pre>