  We present a spectral analysis of XMM-Newton data of ten dwarf novae, nine of
which were observed during a quiescent state. The X-ray spectra indicate the
presence of a hot, optically thin plasma with a temperature distribution
consistent with a simple, isobaric cooling flow. The likely origin of the X-ray
emission is cooling plasma in the boundary layer settling onto the white dwarf.
Using a cooling flow model, we derive the temperatures, accretion rates,
rotational velocities, and elemental abundances of the X-ray emitting gas. We
discuss the implications of our findings for the structure of the boundary
layer. A comparison of X-ray and ultraviolet luminosities finds no evidence of
underluminous boundary layers in any of the quiescent dwarf novae. The X-ray
spectrum of EI UMa differs significantly from those of the other objects,
showing a strong fluorescent Fe K-alpha line and a strong O VII line triplet.
Based on the observational evidence, we argue that EI UMa is most likely an
intermediate polar and not as previously thought a dwarf nova.
