The galvanomagnetic and thermoelectric properties including Hall effect, electrical resistivity, thermopower, and thermal conductivity have been studied for polycrystalline Mo3Sb7. The temperature dependences of the various physical properties, measured from 2 up to 800 K, was explained supposing an important role of magnetic fluctuations significantly suppressed by the opening of a gap in the spin excitation spectrum. In addition, we propose that magnetic excitations are likely responsible for the exotic temperature dependence of the thermal conductivity in the whole temperature range. The high value of the dimensionless figure of merit ZT achieved at high temperature classifies this p-type metal as one of the best thermoelectric metal discovered up to now.