  We consider generic neutrino dipole portals between left-handed neutrinos,
photons, and right-handed heavy neutral leptons (HNL) with Dirac masses. The
dominance of this portal significantly alters the conventional phenomenology of
HNLs. We derive a comprehensive set of constraints on the dipole portal to HNLs
by utilizing data from LEP, LHC, MiniBooNE, LSND as well as observations of
Supernova 1987A and consistency of the standard Big Bang Nucleosynthesis. We
calculate projected sensitivities from the proposed high-intensity SHiP beam
dump experiment, and the ongoing experiments at the Short-Baseline Neutrino
facility at Fermilab. Dipole mediated Primakoff neutrino upscattering and
Dalitz-like meson decays are found to be the main production mechanisms in most
of the parametric regime under consideration. Proposed explanations of LSND and
MiniBooNE anomalies based on HNLs with dipole-induced decays are found to be
severely constrained, or to be tested in the future experiments.
