code: @Override
      protected void releaseResourceImpl(MailResourcesHolder resource)
      {
          //get transport
          Transport transport=resource.getTransport();
  
          if(transport!=null)
          {
              if(transport.isConnected())
              {
                  try
                  {
                      //close connection
                      transport.close();
                  }       
                  catch(Throwable throwable)
                  {
                      //ignore
                  }
              }
          }
      }
docs: Releases the resource from the connection.
  
  @param   resource
  The resource