Email Database Health: Metrics and Maintenance
Six health metrics with target ranges, and what each one is warning you about before delivery drops.
On this page
The short version
- Six metrics with target ranges, each of which moves before delivery does. They are early warnings rather than outcomes.
- The one that matters most is the engaged share, because it drives everything the mailbox providers score you on.
- Track them monthly against your own trailing figures. Published targets vary too much to act on directly.
List health is measured with different numbers from campaign performance. Open and click rates describe how a send did; these describe whether the list is in a state to receive sends at all.
All six move before deliverability does, which is what makes them worth watching. By the time placement drops, several of these have been drifting for months.
The six metrics
| Metric | Healthy range | Warns you about |
|---|---|---|
| Engaged share | Above 50% of the mailable list | Ratios that drive placement |
| Complaint rate | Under 0.1%, per segment | Imminent filtering — the hard ceiling |
| Hard bounce rate | Under 1% on a routine send | A bad acquisition source |
| Net growth, split | Adds exceeding removals | Churn hidden behind a net figure |
| Unsubscribe rate | Under 0.5% on a normal send | Cadence or relevance drifting |
| Unconfirmed or unattributed share | Under 5% | Consent gaps and stale imports |
The engaged share is the one to lead with
It is the proportion of the mailable list that has clicked within your engagement window. Everything mailbox providers score is a ratio, and this is the number those ratios are made of.
It is also the metric that reveals the most about the programme as a whole. A falling engaged share while acquisition is healthy means either the content has stopped landing or the acquisition sources have changed quality — and splitting by lead source distinguishes those in a few minutes.
Report it instead of total subscribers wherever you can. A count that includes people who will never open anything is measuring storage, not audience.
Why the unattributed share matters
The proportion of your list with no recorded source is a measure of how much you cannot reason about. Those subscribers cannot be compared by acquisition route, cannot be traced when a cohort behaves oddly, and cannot be evidenced if consent is ever questioned.
It should fall over time as new signups are tagged and old untagged ones are sunsetted. A rising figure means a capture point is not recording source — usually a new form, an integration, or an import that skipped the field.
That makes it a useful canary for capture problems generally, because the source field is the one most likely to be omitted when someone adds a new signup path in a hurry.
Track them against yourself
The ranges above are starting points and every one of them varies by industry, list size, consent method and cadence. A figure that would be alarming on one list is normal on another.
What is not ambiguous is direction. A metric moving steadily in the wrong direction over three months is a signal regardless of where it sits in a published range, and a metric holding steady is fine even if it looks poor against someone else's benchmark.
So plot them monthly, keep thirteen months so the same month last year is visible, and set the alert on the trend rather than the threshold.
Health review
- All six recorded monthly, on one page
- Engaged share reported instead of total subscribers
- Complaint rate reviewed per segment, not just overall
- Growth split into adds and removals
- Unattributed share falling, not rising
- Thirteen months kept so seasonality is visible
- Alerts set on direction rather than on a fixed threshold
Frequently asked questions
What if the engaged share is far below 50%?
It is common on lists that have never been sunsetted, and it is fixable — a win-back sequence followed by removal moves it substantially in one quarter. The number is a description of accumulated neglect rather than a verdict.
How do I calculate engaged share if opens are unreliable?
Use clicks within your engagement window as the numerator and the mailable list as the denominator. Opens can be a secondary indicator; they should not be the definition.
Should these go in the main report?
One of them — the engaged share — belongs alongside the campaign metrics. The other five belong in a monthly health review, because they are diagnostic rather than performance figures.