  Impurities with the pronounced forward scattering (FS impurities) change
analytical properties of the quasiparticle Green's function substantially
compared to the isotropic scattering. By assuming that the superconducting
pairing is due to the forward E-P scattering (FEP pairing) it is shown that the
critical temperature of clean systems T_{c0} depends linearly on the E-P
coupling constant \lambda and the isotope effect \alpha is small. The FS
impurities make \alpha =1/2 in the dirty limit and affect in the same way the
s- and d-wave FEP pairing. The FS impurities are pair-weakening in both pairing
channels. The usual isotropic impurity scattering is pair-weakening for the
s-wave and pair-breaking for the d-wave FEP pairing.
