  The phenomenology of the most general lepton mass matrices obtained through
weak basis transformations has been discussed. Using a hierarchical
parametrization of these mass matrices, the exact relations for lepton mixing
angles have been obtained assuming normal neutrino mass hierarchy and natural
structures of lepton mass matrices. The recent three neutrino oscillation data
together with the condition of naturalness on Dirac lepton mass matrices
provide a lower bound on the lightest neutrino mass of m{\nu}1 > 3 meV along
with a non-vanishing Dirac CP violating phase.
