title: Sendgrid api substitutions not working for multiple emails
body: <p>how to send email to multiple recipents with substitutions in sendgrid email in c# ?
  Sendgrid api substitutions are not working for multiple receipents.
  I am using Sendgrid to send emails with templates that contain multiple variables. Everything works well when I have only one recipient for an email.</p>
  
  <p>When I have multiple recipients either in To or one in To and one in Cc, the first email is ok but the following have empty strings in the substition tags.</p>
  
  <p>Below is my code : </p>
  
  <pre><code>var message = new SendGridMessage();
  message.Subject = fullName + " has shared SmartForm with you for  " + PLConstants.APP_NAME;
  message.EnableTemplateEngine(PLConstants.SEND_SMARTFORM_EMAIL_TOUSER);
  
  if (!string.IsNullOrEmpty(emailIds))
  {
      string[] bccAddressField = emailIds.Split(',');                    
  
      for (int icount = 0; icount &lt; bccAddressField.Length; icount++)
      {
          if (bccAddressField[icount].ToString() != "")
          {
              if (message.To.Length == 0)
              {
                  message.AddTo(bccAddressField[icount].ToString());
              }
              else
              {
                  //message.AddTo(bccAddressField[icount].ToString());
                  message.AddBcc(new EmailAddress(bccAddressField[icount].ToString()).ToString());
              }
          }
      }
  }
  
  string profileUrl = string.Format("{0}{1}", PLConstants.SMARTLINK_URL,(HttpContext.Current.Session[PLConstants.SESSION_USERNAME].ToString()));
  message.AddSubstitution("{SenderName}",new List&lt;string&gt; { (HttpContext.Current.Session[PLConstants.SESSION_FIRST_NAME].ToString()) });
  message.AddSubstitution("{SmartListingName}", new List&lt;string&gt; { objSmartListingModel.Title });
  message.AddSubstitution("{SmartListingLink}", new List&lt;string&gt; { smartListingLink });
  message.AddSubstitution("{SmartListingRedirectionLink}", new List&lt;string&gt; { smartListingRedirectionLink });
  
  message.Html = " ";
  Mailer.SendEmail(message);
  </code></pre>