  We consider spin accumulation at a ferromagnet--normal metal interface in the
presence of magnetic scattering in the normal metal. In the classical regime,
we discuss the inverse Drude scaling of the conductance as a function of the
interface transparencies. We present a treatment based on an exact solution of
the Boltzmann equation. In the quantum regime, we solve a single impurity
``spin-flip Fabry Perot interferometer'' for quantum coherent multiple
scatterings, in which we find a resonance in the spin flip channels. This
resonance appears to be the quantum analog of the semi classical inverse Drude
scaling of the conductance.
