Yes, but ... we know of several examples of great disappointment: the Post Office is closed on the day of arrival, or the packages arrive after long wanderings or not at all. "What now?"
Sometimes pilgrims send things ahead because it is forbidden to take them on the plane. It might be good to know that there are two good stores in Saint-Jean especially for pilgrims, with a wide range of equipment: Direction Compostelle and Boutique du Pèlerin. During the season these shops are open every day.