  We provide the first systematic study of the viable parameter space for
leptogenesis in the type-I seesaw model with three right-handed neutrinos whose
Majorana masses lie below the electroweak scale. We highlight the very rich
phenomenology of this scenario and discuss several mechanisms that can help to
enhance the baryon asymmetry of the Universe. This allows for much larger heavy
neutrino mixing angles than in the minimal scenario with two heavy neutrinos,
resulting in solutions that can be probed with the LHC and other experiments.
The light neutrino masses can be protected from radiative corrections by an
approximate symmetry related to generalised lepton number.
