This document discusses the results of a study on email marketing conducted by Return Path. The key findings were: 1) Email subscribers can be categorized as either "primary" or "secondary" accounts based on their engagement levels. Primary accounts read the most emails and make the most purchases. 2) The study found that primary accounts don't mind receiving up to 5 emails per week from a single marketer, as this increases their opens and engagement by 43%. Secondary accounts also increased opens by 33% when receiving slightly more emails. 3) However, email marketers need to more carefully consider how many emails to send secondary accounts, as these subscribers have lower engagement levels overall. Tailoring email content and measuring on