Back in August 2013, I wrote a blog on 5 Keys to Email Inbox Delivery, which identified engagement as the Number One key to optimal email delivery. In the blog I briefly touched on how engagement is a metric used to determine which customers are interacting with your emails, and in what ways, such as opening and clicking.

Recently, my team and I came to the realization that we should talk about how engagement affects email deliverability, using the framework of tiers of email engagement to show what those degrees of engagement could mean to you as an email marketer.