  We present a method to identify symmetry groups of the Yukawa sector of the
three-Higgs-doublet model and to determine the implication that the symmetry
has on the lepton masses and mixing. The method can accommodate different
hypotheses about the group representation assignments, and thus support the
exploration of candidate symmetry groups. For one particular representation
selection scheme we apply the computer-implemented method to scan all discrete
groups of order less than 1035. It can be proven that none of these groups
defines a flavor symmetry that implies masses and neutrino mixing angles
consistent with the experimental lepton data, although several cases are found
that are partially or approximately consistent.
