How do I define an "inactive" subscriber?
Still have a question, spotted an error, or have a better explanation or a source we should cite?
There's no universal definition. But there's a way to think about it that actually works for your situation.
An inactive subscriber is someone who hasn't done anything meaningful with your emails in a period that's long enough to matter for your sending reputation. The tricky part is that "long enough" depends on how often you send.
The frequency rule of thumb
If you send daily: consider 30 days of zero engagement as inactive. A daily sender who hasn't opened in a month has had 30 chances. That's a reasonable signal.
If you send weekly: 60 to 90 days. They've seen 8 to 12 emails with no response.
But if you send monthly: 6 months minimum. Don't call someone inactive after missing two monthly newsletters. Life happens.
The opens problem
Opens are no longer a reliable signal. Since Apple's Mail Privacy Protection (MPP) launched in 2021, a large percentage of "opens" are machine-generated. If you're using opens as your only inactivity signal, you're probably keeping more dead addresses than you think.
Clicks are much more reliable. A click requires a real person to make a decision. If someone clicked something in the last 90 days, they're probably real and probably engaged. Prioritize clicks over opens when defining inactivity.
What counts as engagement
Beyond opens and clicks, some ESPs let you track other signals: website visits from email links, purchases, account logins, preference updates. If you have access to these, include them. Someone who bought something from an email three months ago isn't "inactive" even if they haven't clicked a newsletter since.
Define it once, use it consistently
Whatever threshold you pick, stick to it. The worst thing is a vague definition that shifts every time you look at it. Pick your window, document it, and use it consistently for segmentation and re-engagement campaigns.
If you want to check what your current active vs. inactive split actually looks like, email validation can help identify addresses that are structurally dead (bounced, parked domains) vs. addresses that are real but silent.
Contributors
Who worked on this answer
Every name links to their profile. Every company links to their site. Real people, real accountability.
