Enables sphingomyelin phosphodiesterase activity. Involved in ceramide biosynthetic process and sphingomyelin catabolic process. Acts upstream of or within ceramide metabolic process. Located in endoplasmic reticulum membrane and mitochondrial membrane. Orthologous to human SMPD5 (sphingomyelin phosphodiesterase 5 (pseudogene)). [provided by Alliance of Genome Resources, Apr 2022]