  We study the unresolved X-ray emission in three Local Group dwarf elliptical
galaxies (NGC 147, NGC 185 and NGC 205) using XMM-Newton observations, which
most likely originates from a collection of weak X-ray sources, mainly
cataclysmic variables and coronally active binaries. Precise knowledge of this
stellar X-ray emission is crucial not only for understanding the relevant
stellar astrophysics but also for disentangling and quantifying the thermal
emission from diffuse hot gas in nearby galaxies.We find that the integrated
X-ray emissivities of the individual dwarf ellipticals agree well with that of
the Solar vicinity, supporting an often assumed but untested view that the
X-ray emissivity of old stellar populations is quasi-universal in normal
galactic environments, in which dynamical effects on the formation and
destruction of binary systems are not important. The average X-ray emissivity
of the dwarf ellipticals, including M32 studied in the literature, is measured
to be $L_{0.5-2\ \rm {keV}}/M_{\ast} = (6.0 \pm 0.5 \pm 1.8) \times 10^{27} \
\rm{erg \ s^{-1} \ M_\odot^{-1}}$. We also compare this value to the integrated
X-ray emissivities of Galactic globular clusters and old open clusters and
discuss the role of dynamical effects in these dense stellar systems.
