This paper is concerned with the theory on the rest mass of the photon. The equations for the energy of the photon are developed. The theory predicts an equation for the “massive” photoelectric effect similar to the Einstein's original photoelectric effect. This new theory predicts that the value of the black hole's cutoff radius is a function of the frequency of the photons generated inside the black hole. This means that the black hole's event horizon is not a spherical surface but a three-dimensional shell. Because this formulation is not a gravity theory but a theory on massive photons, it cannot predict exactly the same Schwarzchild radius as general relativity. Despite of not being a gravity theory, this theory predicts that, should the equivalent mass of the photon equal its rest mass, the black hole cutoff radius would be equal to the Schwarzchild radius. I am convinced that the full potential of this formulation will be shown when it is used in conjunction with the Proca equations, the standard model and quantum gravity theories.