Email KPIsMeasuring the asset, not the send

The problem with email reporting#

Most email reports are campaign reports: this newsletter achieved this open rate, that promotion this click rate. They answer 'how did last Tuesday go?' and not 'is our email programme getting more or less valuable?'. The second question is the one leaders care about, and it needs different metrics.

Add to this the decline of the open rate as a reliable signal. Privacy features in some mail apps load emails, including the tracking pixel, before the person reads them, which records an open regardless. Open rates have become inflated and uneven across audiences. A framework built on them is built on sand.

A hierarchy of email metrics#

Level one and two: list and health#

These metrics tell you whether the foundation is sound. Track list growth by source, because a source that brings many subscribers who never engage is a liability. Track the active share of the list, defined as people who have clicked or bought within a period that suits your buying cycle.

For health, watch hard bounce rate, complaint rate and unsubscribe rate per send and as trends. Use mailbox providers' postmaster tools for their view of your reputation. Sudden changes here explain more performance drops than any creative decision. See email deliverability.

Level three: engagement that means something#

Click rate, clicks divided by delivered emails, is now the most dependable engagement metric. It reflects a deliberate act. Replies are an underused signal, especially for B2B and editorial email; they indicate real attention and help reputation.

Opens still have uses, for instance spotting a sharp, uniform drop that suggests a deliverability problem, but treat them as a rough directional signal and never as the success measure for a test or a campaign.

Level four and five: conversion and outcomes#

Revenue per recipient (or conversions per recipient for non-commerce goals) is the single most useful campaign metric, because it combines engagement and conversion into one number that can be compared across sends of different sizes. Above that sits the programme view: revenue, retention or pipeline per subscriber over time, and the incremental effect of email measured against holdouts.

The attribution question#

Email platforms attribute revenue generously, often crediting any purchase made within a window after an email was opened or clicked. Since opens are unreliable, open-based attribution is especially inflated. Prefer click-based attribution with a stated window, reconcile with your analytics platform and, for important decisions, use holdout groups.

A holdout is simple: a random slice of the audience does not receive a campaign or automation, and the difference in outcomes between recipients and holdout is the incremental effect. It is the most honest number in email. Our guides to incrementality testing and marketing attribution go further.

The funnel view of a single send#

Different reports for different readers#

Email metrics should feed into your wider marketing KPIs and marketing dashboards rather than live in a separate silo. That is how email gets credit for its role in retention and assisted conversions.

Metrics to demote or retire#

A shorter report is usually a better report. Several metrics still appear in email dashboards out of habit, and they distract from the numbers that matter. We would demote them from headline status, keeping them only as diagnostic signals that an operator glances at when something looks wrong.

• Open rate as a success measure. Keep it only to spot sudden, uniform drops that hint at a placement problem.
• Total list size. A large list with a small active share is a cost, not an asset. Report active subscribers instead.
• Delivered rate on its own. It is almost always high and says nothing about inbox placement.
• Click-to-open rate where opens are unreliable. If the denominator is inflated, the ratio misleads. Use it only for audiences where you can trust opens.
• Campaign-level revenue without a window. A revenue figure means nothing until you state the attribution rule behind it.

Retiring a metric does not mean deleting the data. It means it no longer appears on the page leaders read, so it no longer shapes decisions it was never fit to make.

Setting targets without borrowed benchmarks#

Teams often ask what a good click or conversion rate is. Published averages are tempting, but they blend industries, list qualities, email types and measurement methods that have little in common with yours. A newsletter to engaged professionals and a flash-sale blast to a cold retail list are not comparable, and a single average hides that.

Your own history is the better benchmark. Take the last two or three quarters, split by email type and segment, and set targets as improvements on your own baseline. A welcome email should be compared with previous welcome emails, not with the industry's promotional campaigns. Where you need an external reference, use it to ask questions rather than to set goals.

Three habits keep targets honest. Fix the attribution rule before the quarter starts so results are not reinterpreted afterwards. Separate automation metrics from campaign metrics, because automations reach people at moments of intent and will almost always look stronger. And set at least one health target, such as a ceiling on complaints or a floor on the active share of the list, so that revenue targets cannot be met by burning through the audience.

Turning metrics into decisions#

A metric earns its place on the report only if a change in it would change what you do. Before adding any number, write down the action it would trigger: a falling active share prompts a review of signup sources and sunset rules; rising complaints in one segment prompts a pause and a targeting review; revenue per recipient falling in an automation prompts a content and offer refresh. If no one can name the action, the metric is decoration.

Keep a short log of decisions taken because of the numbers. Over a year, that log is the best evidence that measurement is doing its job, and the clearest guide to which metrics deserve to stay.

Measure email as an asset you are growing, not as a series of sends you are surviving.

Published by Fabulous.Media, a network of specialist marketing agencies. Updated 9 October 2026. Platform features change often; check current official documentation before acting on platform-specific detail.