Can an Infrared-vanishing Gluon propagator Confine Quarks?
  It is shown that the solution of the quark Dyson-Schwinger equation in QCD obtained with a gluon propagator of the form $D(q) \sim q^2/[q^4+b^4]$ and a quark-gluon vertex that is free of kinematic singularities does not describe a confined particle and that there is always a value of $b^2 = b^2_c$ such that chiral symmetry is not dynamically broken for $b^2>b_c^2$. 
Craig D. Roberts