$arPOST = array(
            'ENTITY_TYPE_ID' => 2, //Тип - сделка
            'ENTITY_ID' => 246, //ID сделки
                       'MESSAGE' => 'Текст мессаджа',
            'TITLE' => 'Заголовок, но он вроде не выводится',
            'USER_ID' =>1, //От какого Юзера коммент

        );
        $message_id = \CCrmLiveFeed::CreateLogMessage($arPOST);

   $entity_type = 'LEAD';
   $entity_id = '13308';
   $now = ConvertTimeStamp(time() + CTimeZone::GetOffset(), 'FULL', 's1');
    $arBindings[] = array(
                'OWNER_TYPE_ID' => CCrmOwnerType::ResolveID($entity_type),
                'OWNER_ID' => $entity_id
            );
   $arFields = array(
      'OWNER_ID' => $entity_id,
      'OWNER_TYPE_ID' => CCrmOwnerType::ResolveID($entity_type),
      'TYPE_ID' =>  CCrmActivityType::Email,
      'SUBJECT' => 'ФАЙЛ',
      'START_TIME' => $now,
      'END_TIME' => $now,
      'COMPLETED' => 'Y',
      'RESPONSIBLE_ID' => $USER->GetID(),
      'PRIORITY' => CCrmActivityPriority::Medium,
      'DESCRIPTION' => 'Тестирование записи в лид',
      'DESCRIPTION_TYPE' => CCrmContentType::BBCode,
      'DIRECTION' => CCrmActivityDirection::Outgoing,
      'LOCATION' => '',
      'NOTIFY_TYPE' => CCrmActivityNotifyType::None,

      'BINDINGS' => array_values($arBindings)
   );


   $test = CCrmActivity::Add($arFields, false, false, array('REGISTER_SONET_EVENT' => true));