In the Third Age of Email Deliverability, Engagement Matters

Unlike in the First Age of Email Deliverability when there were no rules or in the Second Age when negative metrics like complaints determined inbox placement, in the Third Age senders’ emails must not only be tolerated by subscribers but occasionally engaged with to avoid being junked or blocked at either the individual or global level. In other words, the need for list quality now keeps list size ambitions in check.

However, an ISP panel at the Email Evolution Conference earlier this month seems to have muddied the water on whether email engagement affects deliverability and inbox placement. The two quasi-revelations from the panel — which included representatives from Gmail,, AOL, and Comcast—were that:

  1. Clicks don’t affect deliverability.
  2. Only spam complaints factor into blocking decisions at

While not news to those in the deliverability community, these two things surprised many and caused some to question the recent emphasis that’s been placed on engagement metrics. Don’t be confused. Here’s why you should still be concerned about engagement and inactive subscribers:

Clicks Are a Proxy: In an interview last year, Gmail’s Sri Somanchi (who was on this EEC panel as well) revealed that they use “literally hundreds of signals to decide whether an email should go to the Inbox or the Spam folder.” However, of those, marketers can only see opens (when images render) and replies (which we’ve trained consumers not to do). Measuring clicks is a proxy for all the metrics marketers just can’t measure.

Junked Is as Bad as Blocked: While doesn’t factor engagement metrics into their sender reputations, engagement metrics do affect individual inbox placement at the inbox provider. While technically different, having your emails junked because of low engagement has nearly the same effect as having them blocked since most people rarely engage with emails in their junk folder.

The Proof Is the Remediation: If you’ve worked at a brand that has had major deliverability problems, you probably have zero doubts about the risk associated with inactive subscribers. That’s because purging and re-permissioning inactives have been a big part of remediation for several years now. Boosting list engagement is a proven component of getting back into the good graces of ISPs and getting blocks removed.

Better Safe than Sorry: Do you lose out on some email marketing revenue by erring on the side of list quality? Sure. But you risk more by erring on the side of list size.

ISPs are careful not to reveal too much about their filtering algorithms to avoid gamesmanship and to keep spammers guessing. However, they have been very clear that engagement matters, whether it’s in global filtering or individual-level filtering. It’s up to marketers to heed those warnings and respond appropriately to inactivity.

For all the details on this issue, check out the full column on

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