Soft shadow for the sun in Yafray

As long as I understand, the usual solution to light an interior with Yafray is:

  • A blue world for the sky
  • An arealight in each window, with the same colour of the sky
  • A yellowish spot (or sunlight) for the sun.
    This produces raytraced, hard, shadows for the sun. But I’d like this shadows to soften with the distance.
    How can this be achieved?