  We discuss the special role of right-handed neutrinos in the $\mu\nu$SSM for
solving the $\mu$- and $\nu$-problems, simultaneously avoiding the potential
domain wall and tadpole problems, In particular, embedding the $\mu\nu$SSM in
the framework of superstrings implies that not all gauge invariant terms are
necessarily present in the superpotential, and thus there is more flexibility
to allow only those that avoid the domain wall and tadpole problems to be
present. These can be non-renormalizable terms of dimension 4 or terms of
higher dimensions. In addition, non-perturbative effects can also solve both
problems. We discuss another implication of the superstring inspired
$\mu\nu$SSM, since the right-handed neutrino is expected to have extra $U(1)$
charges at high energies. In this case, the cubic right-handed neutrino terms
in the superpotential, helpful for generating Majorana masses and solving
domain wall and tadpole problems, can arise through a variety of stringy
mechanisms.
