  Leptogenesis can successfully explain the matter-antimatter asymmetry via
out-of-equilibrium decays of heavy Majorana neutrinos in the early Universe. In
this article, we focus on non-resonant thermal leptogenesis and the possibility
of lowering its scale. In order to do so, we calculate the lepton asymmetry
produced from the decays of one and two heavy Majorana neutrinos using
three-flavoured density matrix equations in an exhaustive exploration of the
model parameter space. We find regions of the parameter space where thermal
leptogenesis is viable at intermediate scales, $T\sim 10^{6}$ GeV. However, the
viability of thermal leptogenesis at such scales requires a certain degree of
cancellation between the tree and one-loop level contribution to the light
neutrino mass matrix and we quantify such fine-tuning.
