Regarding Epsom Salts (magnesium sulfate), I think people should only take sulfates, of any kind, seldom. I've used it a few times when I'm having difficulty purging. I've heard that salts baths are good though.
To relieve constipation, I take other forms of magnesium. Magnesium is well known to draw liquid into the intestines with it. That softens the stool only. It does not stimulate the bowel movement. Most people are deficient in magnesium; because it is not easily assimilated. My favorite for intestinal problems is magnesium citrate. Other forms are oxide, chloride (excellent), aspartate, succinate, and amino acid chelate. LifeExtension company has a product that includes all of these except citrate.