  We consider leptogenesis in scenarios with many neutrino singlets. We find
that the lower bound for the reheating temperature can be significantly relaxed
with respect to the hierarchical three neutrino case. We further argue that the
upper bound for the neutrino mass scale from leptogenesis gets significantly
lifted in these scenarios. As a specific realization, we then discuss an
extra-dimensional model, where the large number of neutrinos is provided by
Kaluza-Klein excitations.
