title: GMAIL SMTP : A call to SSPI failed exception - The function requested is not supported
body: <p>I am sending a mail using gmail smtp :
  Host : smtp.gmail.com
  Port : 587</p>
  
  <p>Getting exception while sending mail using gmail smtp in MVC application.
  Below code used to send mail :</p>
  
  <pre><code>public static int SendMail(string StrFromAdd, string StrEmailTo, string StrSubject, string StrContents,
          string SMTPServer, int SMTPPort, string SMTPUserName, string SMTPPassword,
          string attachment = "", string CC = "", string BCC = "")
      {
          try
          {
              AlternateView AV = null;
              System.Net.Mail.SmtpClient smtpClient = new System.Net.Mail.SmtpClient();
              System.Net.Mail.MailMessage message = new System.Net.Mail.MailMessage();
              System.Net.Mail.MailAddress fromAddress = new System.Net.Mail.MailAddress(StrFromAdd, "Test");
              smtpClient.Host = SMTPServer;
              smtpClient.Port = SMTPPort;
              smtpClient.Credentials = new System.Net.NetworkCredential(SMTPUserName, SMTPPassword);
  
              smtpClient.EnableSsl = true;
  
              message.From = fromAddress;
  
              if (attachment != null)
              {
                  string[] attachmentsarr = attachment.Split(';');
                  foreach (string attach in attachmentsarr)
                  {
                      if (attach != "")
                          message.Attachments.Add(new Attachment(attach));
                  }
              }
  
              string pattern = @"^((([\w]+\.[\w]+)+)|([\w]+))@(([\w]+\.)+)([A-Za-z]{1,3})$";
  
              if (StrEmailTo != "")
              {
                  if (StrEmailTo.IndexOf(',') &gt; -1)
                  {
                      string[] _strArrstrEmailTo = StrEmailTo.Split(',');
                      foreach (object objBCCEmailID in _strArrstrEmailTo)
                          if (Regex.IsMatch(objBCCEmailID.ToString().Trim(), pattern))
                              message.To.Add(new System.Net.Mail.MailAddress(objBCCEmailID.ToString().Trim()));
  
                  }
                  else
                      message.To.Add(new System.Net.Mail.MailAddress(StrEmailTo.ToString().Trim()));
              }
  
              if (CC != "")
              {
                  if (CC.IndexOf(',') &gt; -1)
                  {
                      string[] _strArrstrEmailCC = CC.Split(',');
                      foreach (object objBCCEmailID in _strArrstrEmailCC)
                          if (Regex.IsMatch(objBCCEmailID.ToString().Trim(), pattern))
                              message.CC.Add(new System.Net.Mail.MailAddress(objBCCEmailID.ToString().Trim()));
  
                  }
                  else
                      message.CC.Add(new System.Net.Mail.MailAddress(CC.ToString().Trim()));
              }
  
              if (BCC != "")
              {
                  if (BCC.IndexOf(',') &gt; -1)
                  {
                      string[] _strArrstrEmailBCC = BCC.Split(',');
                      foreach (object objBCCEmailID in _strArrstrEmailBCC)
                          if (Regex.IsMatch(objBCCEmailID.ToString().Trim(), pattern))
                              message.Bcc.Add(new System.Net.Mail.MailAddress(objBCCEmailID.ToString().Trim()));
  
                  }
                  else
                      message.Bcc.Add(new System.Net.Mail.MailAddress(BCC.ToString().Trim()));
              }
              // This is added for custom form &amp; email template image
              List&lt;string&gt; ImageFiles = Common.GetImagesInHTMLString(StrContents);
              if (ImageFiles != null &amp;&amp; ImageFiles.Count &gt; 0)
              {
                  string addStrContents = string.Empty;
  
                  for (int i = 0; i &lt; ImageFiles.Count; i++)
                  {
                      // this is for custom form
                      if (ImageFiles[i].Contains("CustomFormImage"))
                      {
                          string Path = Regex.Match(ImageFiles[i], "&lt;img.+?src=[\"'](.+?)[\"'].+?&gt;", RegexOptions.IgnoreCase).Groups[1].Value;
                          int pos = Path.LastIndexOf("\\") + 1;
                          string FullPath = HttpContext.Current.Server.MapPath("~/img/CustomFormImage/" + Path.Substring(pos, Path.Length - pos));
                          if (System.IO.File.Exists(FullPath))
                          {
                              //addStrContents = addStrContents + "&lt;img style='width:100px;height:100px;' src=\"cid:" + Path.Substring(pos, Path.Length - pos).Split('.')[0] + "\"&gt;" + Environment.NewLine;
                              StrContents = StrContents.Replace(Path, "cid:" + Path.Substring(pos, Path.Length - pos).Split('.')[0]);
                          }
                      }
                      // this is for email template image
                      else if (ImageFiles[i].Contains("EmailHeaderFooterImgs"))
                      {
                          string Path = Regex.Match(ImageFiles[i], "&lt;img.+?src =[\"'](.+?)[\"'].+?&gt;", RegexOptions.IgnoreCase).Groups[1].Value;
                          int pos = Path.LastIndexOf("\\") + 1;
                          if (System.IO.File.Exists(Path))
                          {
                              //addStrContents = addStrContents + "&lt;img style='width:100px;height:100px;' src=\"cid:" + Path.Substring(pos, Path.Length - pos).Split('.')[0] + "\"&gt;" + Environment.NewLine;
                              StrContents = StrContents.Replace(Path, "cid:" + Path.Substring(pos, Path.Length - pos).Split('.')[0]);
                          }
                      }
                  }
                  AV = AlternateView.CreateAlternateViewFromString(StrContents, null, MediaTypeNames.Text.Html);
                  for (int i = 0; i &lt; ImageFiles.Count; i++)
                  {
                      // this is for custom form
                      if (ImageFiles[i].Contains("CustomFormImage"))
                      {
                          string Path = Regex.Match(ImageFiles[i], "&lt;img.+?src=[\"'](.+?)[\"'].+?&gt;", RegexOptions.IgnoreCase).Groups[1].Value;
                          int pos = Path.LastIndexOf("\\") + 1;
                          string FullPath = HttpContext.Current.Server.MapPath("~/img/CustomFormImage/" + Path.Substring(pos, Path.Length - pos));
                          if (System.IO.File.Exists(FullPath))
                          {
                              //FileStream fs = new FileStream(FullPath, FileMode.Open, FileAccess.Read);
                              //Attachment a = new Attachment(fs, Path.Substring(pos, Path.Length - pos), MediaTypeNames.Application.Octet);
                              //message.Attachments.Add(a);
                              //addStrContents = addStrContents + "&lt;img src=\"cid:" + Path.Substring(pos, Path.Length - pos).Split('.')[0] + "\"&gt;" + Environment.NewLine;
                              LinkedResource Img = new LinkedResource(FullPath, MediaTypeNames.Image.Jpeg);
                              Img.ContentId = Path.Substring(pos, Path.Length - pos).Split('.')[0];
                              AV.LinkedResources.Add(Img);
                          }
                      }
                      // this is for email template image
                      else if (ImageFiles[i].Contains("EmailHeaderFooterImgs"))
                      {
                          string Path = Regex.Match(ImageFiles[i], "&lt;img.+?src =[\"'](.+?)[\"'].+?&gt;", RegexOptions.IgnoreCase).Groups[1].Value;
                          int pos = Path.LastIndexOf("\\") + 1;
                          if (HttpContext.Current != null)
                          {
                              string FullPath = HttpContext.Current.Server.MapPath("~/EmailHeaderFooterImgs/" + Path.Substring(pos, Path.Length - pos));
                              if (System.IO.File.Exists(Path))
                              {
                                  LinkedResource Img = new LinkedResource(Path, MediaTypeNames.Image.Jpeg);
                                  Img.ContentId = Path.Substring(pos, Path.Length - pos).Split('.')[0];
                                  AV.LinkedResources.Add(Img);
                              }
                          }
                      }
                  }
              }
  
              message.Subject = StrSubject;
              message.IsBodyHtml = true;
              if (AV != null)
                  message.AlternateViews.Add(AV);
              else
                  message.Body = StrContents;
  
              smtpClient.Send(message);
              message.Dispose();
              return 1;
          }
          catch (Exception ex)
          {
  
          }
      }
  </code></pre>
  
  <p>Below is stack track :</p>
  
  <pre><code>    System.Security.Authentication.AuthenticationException: A call to SSPI failed, see inner exception. System.ComponentModel.Win32Exception: The function requested is not supported
     at System.Net.Security.SslState.StartSendAuthResetSignal(ProtocolToken message, AsyncProtocolRequest asyncRequest, Exception exception)
     at System.Net.Security.SslState.CheckCompletionBeforeNextReceive(ProtocolToken message, AsyncProtocolRequest asyncRequest)
     at System.Net.Security.SslState.ProcessReceivedBlob(Byte[] buffer, Int32 count, AsyncProtocolRequest asyncRequest)
     at System.Net.Security.SslState.StartReceiveBlob(Byte[] buffer, AsyncProtocolRequest asyncRequest)
     at System.Net.Security.SslState.CheckCompletionBeforeNextReceive(ProtocolToken message, AsyncProtocolRequest asyncRequest)
     at System.Net.Security.SslState.ForceAuthentication(Boolean receiveFirst, Byte[] buffer, AsyncProtocolRequest asyncRequest)
     at System.Net.Security.SslState.ProcessAuthentication(LazyAsyncResult lazyResult)
     at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
     at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
     at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
     at System.Net.TlsStream.ProcessAuthentication(LazyAsyncResult result)
     at System.Net.TlsStream.Write(Byte[] buffer, Int32 offset, Int32 size)
     at System.Net.Mail.SmtpConnection.Flush()
     at System.Net.Mail.ReadLinesCommand.Send(SmtpConnection conn)
     at System.Net.Mail.EHelloCommand.Send(SmtpConnection conn, String domain)
     at System.Net.Mail.SmtpConnection.GetConnection(ServicePoint servicePoint)
     at System.Net.Mail.SmtpClient.GetConnection()
     at System.Net.Mail.SmtpClient.Send(MailMessage message)
     at MVC.Common.SendMails.SendMail(String StrFromAdd, String StrEmailTo, String StrSubject, String StrContents, String SMTPServer, Int32 SMTPPort, String SMTPUserName, String SMTPPassword, String attachment, String CC, String BCC) in SendMails.cs:line 296
  </code></pre>
  
  <p>Note : Same code is working in another application which is hosted in same server and also used same gmail configuration to send mails.</p>