  There has been recent interest in understanding the all loop structure of the
subleading power soft and collinear limits, with the goal of achieving a
systematic resummation of subleading power infrared logarithms. Most of this
work has focused on subleading power corrections to soft gluon emission, whose
form is strongly constrained by symmetries. In this paper we initiate a study
of the all loop structure of soft fermion emission. In $\mathcal{N}=1$ QCD we
perform an operator based factorization and resummation of the associated
infrared logarithms, and prove that they exponentiate into a Sudakov due to
their relation to soft gluon emission. We verify this result through explicit
calculation to $\mathcal{O}(\alpha_s^3)$. We show that in QCD, this simple
Sudakov exponentiation is violated by endpoint contributions proportional to
$(C_A-C_F)^n$ which contribute at leading logarithmic order. Combining our
$\mathcal{N}=1$ result and our calculation of the endpoint contributions to
$\mathcal{O}(\alpha_s^3)$, we conjecture a result for the soft quark Sudakov in
QCD, a new all orders function first appearing at subleading power, and give
evidence for its universality. Our result, which is expressed in terms of
combinations of cusp anomalous dimensions in different color representations,
takes an intriguingly simple form and also exhibits interesting similarities to
results for large-x logarithms in the off diagonal splitting functions.
