Catalyzes the addition of a phosphoethanolamine moiety to the lipid A. The phosphoethanolamine modification is required for resistance to polymyxin. Bacterial outer membrane biogenesis; LPS lipid A biosynthesis. The eptA-basRS operon is positively autoregulated by BasR under high iron or aluminum concentration conditions. Belongs to the phosphoethanolamine transferase family. EptA subfamily.