  Some tails of ram-pressure stripped galaxies are detected in HI, some in
Halpha, and some in X-ray (but never all three so far). We use numerical
simulations to probe the conditions for the production of X-ray bright tails,
demonstrating that the primary requirement is a high pressure intracluster
medium (ICM). This is because the stripped tail is mostly in pressure
equilibrium with the ICM, but mixing leaves it with densities and temperatures
intermediate between the cold gas in the disk and the hot ICM. Given a high
enough ICM pressure, this mixed gas lies in the X-ray bright region of the
phase diagram. We compare the simulations to observations of the ram pressure
stripped tail of ESO 137-001, showing excellent agreement in the total measured
X-ray and Halpha emission and non-flaring morphology of the tail, and
consistent HI measurements. Using these comparisons we constrain the level of
mixing and efficiency of heat conduction in the intracluster medium (ICM)
