This document discusses strategies for optimizing email marketing, including managing send frequency. It notes that sending too frequently can reduce engagement and increase unsubscribes, while sending too infrequently misses opportunities. The ideal frequency varies per subscriber based on their past behaviors and brand relationships. Return Path analyzes individual subscriber data and behavior data from panels to determine the ideal send frequency for each subscriber to balance engagement and risk of unsubscribes. Frequency optimization solutions can increase engagement rates and reduce costs compared to one-size-fits-all approaches.