A precise correspondence between freely-acting orbifolds (Scherk-Schwarz
compactifications) and string vacua with NSNS flux turned on is established
using T-duality.
We focus our attention to a certain non-compact Z_2 heterotic freely-acting
orbifold with N=2 supersymmetry (SUSY). The geometric properties of the T-dual
background are studied. As expected, the space is non-Kahler with the most
generic torsion compatible with SUSY. All equations of motion are satisfied,
except the Bianchi identity for the NSNS field, that is satisfied only at
leading order in derivatives, i.e. without the curvature term. We point out
that this is due to unknown corrections to the standard heterotic T-duality
rules.Comment: 13 pages, no figures; v2: references added and rearranged, version to
appear in JHE