Definition
An email subscriber health score is a composite metric that rates each contact's overall condition and value to the sender, combining engagement, deliverability risk, and commercial signals into a single number. It goes beyond simple engagement by also accounting for factors such as bounce risk, complaint history, and purchase behaviour. The health score helps teams decide which subscribers to protect, which to nurture, and which to suppress.
How It Works
A health score aggregates multiple indicators about a subscriber into one comparable value. The exact inputs vary by business, but most scores share a common core.
- Engagement signals — opens, clicks, and recency of activity indicate how interested the subscriber currently is.
- Risk signals — hard bounces, spam complaints, and invalid-address flags lower the score, since they threaten deliverability.
- Commercial signals — purchases, order value, and product interest raise the score because they represent realised value.
- Weighting and normalisation — each signal is weighted by importance and mapped to a standard scale, such as 0 to 100.
The score is then used to route subscribers into segments, set send frequency, and trigger re-engagement or suppression actions when a score falls below a threshold. It is a natural complement to an engagement-score, adding risk and value dimensions.
Best Practices
- Define what "healthy" means first — agree on the behaviours that indicate a subscriber is valuable before assigning weights.
- Include risk, not just engagement — a highly engaged address that is also a spam-trap risk is not healthy.
- Recompute on a schedule — health decays and improves constantly, so refresh scores daily or weekly.
- Set action thresholds — map score bands to concrete behaviours, such as "suppress below 20" or "protect above 80."
- Keep the model explainable — the score should be understandable to the team using it, not a black box.
Example
A brand scores subscribers from 0 to 100, weighting clicks and purchases at 60%, opens at 20%, and risk flags at 20% (subtracted). A subscriber who purchased last month and clicks regularly scores 92 and is flagged as high-value. Another with a spam complaint and no opens in a year scores 11 and is added to the suppression-list.
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Frequently Asked Questions
A temperature score focuses on recency and frequency of engagement, while a health score is broader, combining engagement with deliverability risk and commercial value. Health scoring is a superset that answers "is this subscriber an asset or a liability?"
At minimum, engagement signals such as opens and clicks, risk signals such as bounces and complaints, and, where available, commercial signals such as purchases. Additional data can be added as long as it improves the decision the score drives.
Daily or weekly is typical, depending on send volume. The score is only useful if it reflects current behaviour, so stale scores lead to poor routing decisions.
Yes. Subscribers with low scores from inactivity can be re-engaged through win-back campaigns, and addresses flagged as risky can sometimes be recovered through list validation. The score should reflect these improvements when they occur.