Let Omega subset of R-3 be a bounded weak Lipschitz domain with boundary Gamma :- partial derivative Omega divided into two weak Lipschitz submanifolds Gamma(tau) and Gamma(nu) and let epsilon denote an L-infinity-matrix field inducing an inner product in L-2(Omega). The main result of this contribution is the so called Maxwell compactness property, i.e., the Hilbert space {E is an element of L-2(Omega) : rot E is an element of L-2(Omega), div epsilon E is an element of L-2(Omega), nu X E vertical bar Gamma(tau) = 0,nu.epsilon E vertical bar Gamma(nu) = 0} is compactly embedded into L-2(Omega). We will also prove some canonical applications, such as Maxwell estimates, Helmholtz decompositions and a static solution theory. Furthermore, a Fredholm alternative for the underlying time-harmonic Maxwell problem and all corresponding and related results for exterior domains formulated in weighted Sobolev spaces are straight forward.