The longitudinal SSE with an out-of-plane temperature gradient is applicable for ferromagnetic (FM) insulators such as yttrium iron garnet (YIG), where the nonmagnetic metal Pt on the FM insulator as in Pt/YIG is used as a spin current detector. However, our results  show that although the temperature gradient ∇zT is unequivocally out-of-plane, one encounters another issue of Magnetic Proximity Effects (MPE) in Pt when it is in contact with a FM material. The magneto-transport measurements, both electrical and thermal, conclusively demonstrates the existence of MPE in Pt, with further evidences from x-ray magnetic circular dichroism results. More importantly, we observed intrinsic longitudinal SSE without any appreciable MPE in Au/YIG.