  The recent discovery of superconductivity at high pressure in the two-leg
ladder compounds BaFe$_2X_3$ ($X$=S, Se) started the novel field of
quasi-one-dimensional iron-based superconductors. In this publication, we use
Density Functional Theory (DFT) to predict that the previously barely explored
ladder compound RbFe$_2$Te$_3$ should be magnetic with a CX-type arrangement
involving ferromagnetic rungs and antiferromagnetic legs, at the realistic
density of $n=5.5$ electrons per iron. The magnetic state similarity with
BaFe$_2$S$_3$ suggests that RbFe$_2$Te$_3$ could also become superconducting
under pressure. Moreover, at $n=6.0$ our DFT phase diagrams (with and without
lattice tetramerization) reveal that the stable magnetic states could be either
a 2$\times$2 magnetic Block-type, as for $X$=Se, or a previously never observed
before CY-type state, with ferromagnetic legs and antiferromagnetic rungs. In
the Te-based studies, electrons are more localized than in S, implying that the
degree of electronic correlation is enhanced for the Te case.
