  Recently Au\ss enhofer and the author independently have shown that the free
abelian topological group $A(\mathbf{s})$ over a convergent sequence
$\mathbf{s}$ does not admit the strongest compatible locally quasi-convex group
topology that gives the first example of a locally quasi-convex abelian group
without a Mackey group topology. In this note we considerably extend this
example by showing that the free abelian topological group $A(X)$ over a
non-discrete zero-dimensional metrizable space $X$ does not have a Mackey group
topology. In particular, for every countable non-discrete metrizable space $X$,
the group $A(X)$ does not have a Mackey group topology.
