Using the data you have on each of your contacts—such as when they open, click, and convert—and scheduling your emails to send when your contacts are mostly likely to engage with your email is the definition of what?

on Fill in the blank: Return on investment is used in many aspects of your inbound strategy. In your email marketing strategy, it is defined

Understanding implicit and explicit data Sending at the right time Having buyer personas Segmenting by the buyer’s journey