  We consider weak solutions of the inhomogeneous non-cutoff Boltzmann equation
in a bounded domain with any of the usual physical boundary conditions:
in-flow, bounce-back, specular-reflection and diffuse-reflection. When the
mass, energy and entropy densities are bounded above, and the mass density is
bounded away from vacuum, we obtain an estimate of the $L^\infty$ norm of the
solution depending on the macroscopic bounds on these hydrodynamic quantities
only. It is a regularization effect in the sense that the initial data is not
required to be bounded.
