Getting Exception from HRESULT: 0x80072F0D when posting to a service in Windows phone 8.1

When I am trying to post a data to an API using HttpClient in Windows Phone 8.1, I am always getting Exception from HRESULT: 0x80072F0D exception. In fiddler, it works fine.

try
{  
    var requestbody="json data"
    HttpClient httpClient = new HttpClient();
    HttpRequestMessage msg = new HttpRequestMessage(new HttpMethod("POST"), new Uri(addressUri));
    msg.Content = new HttpStringContent(requestbody);
    msg.Content.Headers.ContentType = new HttpMediaTypeHeaderValue("application/json");
    HttpResponseMessage response = await httpClient.SendRequestAsync(msg).AsTask();
}           
catch (Exception ex)
{
    getting **Exception from HRESULT: 0x80072F0D**
}

Please tell me what went wrong?

---FYI----

For getting additional information about the HRESULT code : Follow this WebErrorStatus enumeration

  var exceptionDetail = WebError.GetStatus(ex.GetBaseException().HResult);

  if (exceptionDetail == WebErrorStatus.HostNameNotResolved)
  {
    //
  }

This looks like a certificate related problem. Maybe you are using SSL. While lots of programs gracefully override missing certificates if not explicitly necessary (e.g.: browsers) the HttpClient is pretty sensitive against that.

You should try to download the certificate for the connection you're using and store the cert file in your assets folder. When your app starts, push it into the certificate store. This is a snippet I am using in one of my apps. Maybe this makes your exception go away.

Read more here: http://blogs.msdn.com/b/wsdevsol/archive/2014/06/05/including-self-signed-certificates-with-your-windows-runtime-based-windows-phone-8-1-apps.aspx

// Add our custom certificate
try
{
    // Read the contents of the Certificate file
    System.Uri certificateFile = new System.Uri("ms-appx:///Assets/ca.cer");
    Windows.Storage.StorageFile file = await Windows.Storage.StorageFile.GetFileFromApplicationUriAsync(certificateFile);
    Windows.Storage.Streams.IBuffer certBlob = await Windows.Storage.FileIO.ReadBufferAsync(file);

    // Create an instance of the Certificate class using the retrieved certificate blob contents
    Windows.Security.Cryptography.Certificates.Certificate rootCert = new Windows.Security.Cryptography.Certificates.Certificate(certBlob);

    // Get access to the TrustedRootCertificationAuthorities for your own app (not the system one)
    Windows.Security.Cryptography.Certificates.CertificateStore trustedStore = Windows.Security.Cryptography.Certificates.CertificateStores.TrustedRootCertificationAuthorities;

    // Add the certificate to the TrustedRootCertificationAuthorities store for your app
    trustedStore.Add(rootCert);
}
catch (Exception oEx)
{
   // Catch that exception. We don't really have a choice here..
   var msg = oEx.Message;
}