What metrics define “active” vs “inactive”?
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The answer used to be simple: opens and clicks. Now it's more complicated, because opens aren't what they were.
Clicks: the most reliable signal you have
A click requires a real person to make an intentional decision. It's the gold standard for engagement. If someone clicked something in your email in the last 90 days, they're active. Full stop. Prioritize this metric above everything else when segmenting active vs. inactive.
Opens: treat with caution
Since Apple's Mail Privacy Protection (MPP) rolled out in 2021, a significant chunk of "opens" are machine-generated. Apple pre-fetches email content on behalf of users, which triggers your open pixel even if no human ever read the email. If your list has a large proportion of Apple Mail or iOS users, your open rates are inflated.
Opens still have signal value, but don't treat an open-only subscriber as confidently active. An open with no associated clicks over 6+ months is a weaker signal than you might think.
Other signals worth tracking
If your ESP or CRM supports it, these are all valid engagement signals:
Purchases or conversions attributed to email. Someone who bought something from a campaign three months ago is active, even if they haven't clicked a newsletter since.
Website visits from email links. If you're tracking UTM parameters and someone has been clicking through to your site, that's real engagement.
Account activity. For SaaS or membership products, logins and product usage can supplement email engagement data.
Preference updates or profile changes. If they took the time to update their preferences, they're definitely engaged.
Setting your threshold
Pick the signals you have access to and set a window. Someone is active if they've done any of the above in your chosen window (typically 90 days for weekly senders, longer for monthly). Someone is inactive if they've done nothing in that window.
Then segment. Don't send the same content to actives and inactives. Run re-engagement campaigns for the inactives first. Suppress the ones who don't respond. Your deliverability will thank you.
Not sure how to set this up in your specific ESP? The Review My Emails SOS line can help: reviewmyemails.com/sos.
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