Email frequency is how often you communicate with subscribers. Too infrequent and subscribers forget who you are; too frequent and unsubscribe rates spike. Optimal frequency varies by industry: e-commerce (2-4/week), B2B newsletters (1-2/week), transactional (as-needed), re-engagement (1-3 emails over 2 weeks). Let subscribers choose their frequency preference at signup or in their preferences. MisarMail allows per-subscriber frequency preferences and tracks engagement by send frequency.