code: function setHTMLContent($mailingId, $html, $doImageGrabbing = true, $doLinkTracking = false)
      {
          $queryParameters = array(
              'doImageGrabbing' => ($doImageGrabbing == TRUE) ? "true" : "false",
              'doLinkTracking' => ($doLinkTracking == TRUE) ? "true" : "false"
          );
          return $this->post('mailings/' . $mailingId . '/contents/html', $html, $queryParameters, "text/html");
      }
docs: Updates the HTML content of the mailing referenced by the given ID.
  
  @param string $mailingId
  the ID of the mailing to update
  @param string $html
  the new HTML content of the mailing
  @param bool $doImageGrabbing
  specifies if image grabbing should be performed
  @param bool $doLinkTracking
  specifies if link tracking should be performed
  @return \em com_maileon_api_MaileonAPIResult
  the result object of the API call
  @throws com_maileon_api_MaileonAPIException
  if there was a connection problem or a server error occurred