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At present, cosmological observations set the most stringent bound on the neutrino mass scale. Within the standard cosmological model ($Λ$CDM), the Planck collaboration reports $\sum m_ν< 0.12\,\text{eV}$ at 95% CL. This bound, taken at face value, excludes many neutrino mass models. However, unstable neutrinos, with lifetimes shorter than the age of the universe $τ_ν\lesssim t_U$, represent a particle physics avenue to relax this constraint. Motivated by this fact, we present a taxonomy of neutrino decay modes, categorizing them in terms of particle content and final decay products. Taking into account the relevant phenomenological bounds, our analysis shows that 2-body decaying neutrinos into BSM particles are a promising option to relax cosmological neutrino mass bounds. We then build a simple extension of the type I seesaw scenario by adding one sterile state $ν_4$ and a Goldstone boson $ϕ$, in which $ν_i \to ν_4 \, ϕ$ decays can loosen the neutrino mass bounds up to $\sum m_ν\sim 1\,\text{eV}$, without spoiling the light neutrino mass generation mechanism. Remarkably, this is possible for a large range of the right-handed neutrino masses, from the electroweak up to the GUT scale. We successfully implement this idea in the context of minimal neutrino mass models based on a $U(1)_{μ-τ}$ flavor symmetry, which are otherwise in tension with the current bound on $\sum m_ν$.