Correos only sends to private albergues, pensions or hotels. Or you can pick your bag up at the post office in say, Pontedeume or Betanzos. I have seen others sayin earlier threads that Correos does deliver to the albergue at Hospital de Bruma though.
Unless you book through one of the tour companies who book accommodation and transfer your bags, I think it is Correos and Correos only who deliver. I stayed in pensions on the way, and Correos delivered each and every day. Very god and cheap service, and made a huge difference to the enjoyment of walking. You can even have your bag as a, more secure, suitcase, if you use the Correos bag delivery service.