'Engagement Days' measures your total contacts and the average amount of days since they have last engaged. It is an extremely important metric to monitor in order to maximize your email deliverability.
Providers, like Gmail, want to ensure their users only receive interesting and relevant content in their inbox. If they notice their users are not engaging with your business’s emails, they’ll learn this behavior overtime and begin to send future emails to the junk folder. Even worse, if recipients are no longer interested but continue to receive your content, the likelihood of reporting spam will increase.
When you are not keeping your list clean based on recent engagement: You are likely emailing:
Spam traps (email addresses created for the sole purpose of catching spam)
Invalid email addresses (recipient addresses that do not exist)
However, when you only send emails to engaged recipients, you’re telling providers that you are a trustworthy sender by practicing good list hygiene.