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An analytical formula for the linear complex susceptibility of dipolar assemblies subjected to thermal agitation, long range interactions and an externally applied uniform sinusoidal field of weak amplitude is derived using the forced rotational diffusion equation of Cugliandolo et al. [Phys. Rev. E 91, 032139 (2015)] in the virial approximation. If the Kirkwood correlation factor of the dipolar assembly gK exceeds unity, a thermally activated process arising from the interaction-specific component arises while for gK<1, the susceptibility spectrum normalized by its static value is practically unaltered with respect to that of the ideal gas phase.