A theoretical description of Mossbauer relaxation spectra of the Fe(III) high-spin ion is presented for the general case of rhombic symmetry. A least-squares fit of Mossbauer spectra of the Superoxide Dismutase of Propioni bacterium shermanii subspec. freudenreichii (SOD) is given using this theory. It is shown that an isotropic relaxation model is a sufficiently good model to describe the temperature dependence of the Mossbauer spectra.