Email marketing metrics that tell you what to fix next

This guide covers the email marketing metrics we use to judge a campaign: the formula for each, where it misleads, and how the numbers fit into a report you can read in five minutes. Many monthly reports still lead with open rate, yet for anyone reading in Apple Mail with Privacy Protection turned on, an open no longer proves a person read anything. Unfamiliar terms are defined in our email marketing glossary.

Every formula here follows the same chain as our email revenue calculator: delivered emails, then clicks, then orders, then revenue. Learn that chain and you can trace any revenue drop to the step that broke.

Which email marketing metrics should you track?

Twelve numbers answer almost every question a US business asks about its email program. They fall into three groups: deliverability (delivery, bounce and complaint rates), engagement (opens, clicks, click to open and unsubscribes) and results (conversion, revenue per recipient, order value, list growth and ROI). The table follows roughly the order a subscriber moves through them.

Email marketing KPIs vs metrics: which numbers decide success?

A metric is any number your platform reports. A KPI is the one or two metrics you agreed on before the send that decide whether the campaign worked. Everything else is a diagnostic you check only to explain why the KPI moved. Raw list size and open rate are the usual vanity metrics: easy to inflate, weak at predicting revenue.

Pick the KPI from the email's goal, not from whatever looks best afterward:

• Online sales: revenue per recipient.
• Bookings and appointments: confirmed reservations, counting the ones made by phone.
• Lead generation: form fills or demo requests per 1,000 delivered.
• Apps and software: the in app action the email asked for, such as a first login or a first entry.
• Newsletters: click rate, plus the unsubscribe trend across several issues.

Here is how we would set KPIs for four campaigns from our portfolio of real client emails. These are the measures we choose for each type of brief, not published results.

Half of those KPIs live outside the email platform. Email starts the action and your store, booking system or app finishes it, so tracking setup matters more than any dashboard.

How to calculate email metrics: a worked example

Here is one hypothetical campaign with round numbers, worked line by line. It does not describe any client.

Enter the same inputs in the revenue calculator (20,000 contacts, one campaign, 98.5% delivery, 2% click rate, 3% conversion, $95 order value) and it returns about $1,123. The small gap is rounding in the conversion rate.

Delivery rate is not inbox rate

"Delivered" only means the receiving server accepted the message, not that it reached the inbox. A 99% delivery rate and a spam folder problem can exist together, so authentication and Google Postmaster Tools get checked separately. Our email deliverability checklist covers those checks.

Is click rate the same as click through rate?

Sometimes. Mailchimp defines click rate as the share of delivered emails that registered at least one click. Some tools call that same number click through rate, while others use click through rate for clicks divided by opens, which is really click to open rate. Check the denominator before comparing two reports. Here and in our calculator, click rate means unique clickers divided by delivered emails.

Two kinds of conversion rate

Per click (orders ÷ clickers) tells you how well the landing page and offer worked. Per delivered email (orders ÷ delivered) tells you how well the whole campaign worked. In the example, 12 orders are 3.0% of clickers but 0.06% of delivered emails. Label which one you mean. The calculator uses the per click version, which is why it multiplies click rate by conversion rate.

Revenue per recipient depends on attribution

Revenue per recipient lets you compare a 5,000 person segment with a 50,000 person send fairly, but it is only as good as the rule that credits orders to an email. Klaviyo's attribution guide describes a last touch model that, by default, credits purchases made within 5 days of an email open or click, counted from the send. With open based credit, an Apple Mail preload can claim a sale the email never influenced, so Klaviyo offers a setting to exclude Apple Privacy Protection opens. Pick your window and keep it fixed so months stay comparable.

What did Apple Mail Privacy Protection do to open rates?

Platforms count an open when a tiny invisible image in the email loads from their server. Apple announced Mail Privacy Protection on June 7, 2021 to stop that kind of pixel tracking. According to Apple's privacy page, when a reader turns on Protect Mail Activity, Mail downloads remote content in the background by default, whether or not the reader engages with the email, and routes it through two separate relays that hide the reader's IP address.

So the pixel loads, the platform logs an open, and nobody may have read a word. Apple's iPhone User Guide says the feature prevents senders from seeing whether you opened their message. On an iPhone it sits under Settings > Apps > Mail > Privacy Protection.

What inflated opens break

• Open rate. It tracks the share of your list reading in Apple Mail with the feature on, not subject line quality.
• Click to open rate. Extra opens pad the denominator, so it falls even when the same people click.
• Engaged segments. "Opened in the last 90 days" fills with people who have not read anything in months, and mailing them more often can hurt your sender reputation.
• Subject line A/B tests. A test judged on opens can crown a winner on preloads. Pick clicks or revenue as the winning metric where your platform allows it. Our guide to writing email subject lines covers fair testing.
• Send time and location data. A preload happens when Mail fetches the message, not when someone reads it, and the relay hides where the reader is.
• Open based attribution. Sales get credited to emails nobody read.

How Klaviyo and Mailchimp handle it

Klaviyo adds an Apple Privacy Open property to Opened Email events, set to True when the open came from a device with the feature on. Adding "where Apple Privacy Open is false" to a segment keeps preloads out of your engagement rules. Mailchimp's bot filtering setting, which is on by default, instead hides Apple Mail Privacy Protection opens and bot email clicks across every report, with filtered data back to July 10, 2024 for Apple opens and August 10, 2025 for clicks. Mailchimp warns that open and click numbers drop significantly when you switch it on.

What to do instead

1. Make click rate the headline engagement metric, and build engaged segments on clicks, purchases and site visits.
2. Turn on Apple open or bot filtering, and note the date in your report, because every number after it will step down.
3. Check your platform's email client report for the share of your list reading in Apple Mail. The bigger it is, the less your open rate means.

Why are some email clicks fake too?

Mailchimp lists anti spam security scanners and link preview generators as bot activity that can open emails and click links before your contacts do, and says it usually comes from automated security services. Watch business lists most closely, like the Shopify merchants our Whapi campaign was written for. Warning signs: a burst of clicks seconds after delivery, or one contact clicking every link. Use filtered clicks for conversion math, or your conversion rate will look worse than it is.

What do unsubscribes, complaints and bounces say about list health?

These numbers protect your ability to reach the inbox, so check them after every send. Spam complaint rate and list hygiene are part of the deliverability monitoring in our plan.

Unsubscribe rate

A steady trickle is healthy, since people who leave quietly are not marking you as spam. Look for jumps after a campaign type or a frequency change. Under CAN-SPAM, the FTC says you must honor an opt out request within 10 business days, and your opt out method must keep working for at least 30 days after you send. Process "please remove me" replies too. Our CAN-SPAM compliance checklist lists every requirement.

Spam complaint rate

For Gmail, the number that matters is in Google Postmaster Tools, not your platform. Google tells senders to keep the user reported spam rate below 0.1% and never let it reach 0.3%. Google measures it as the percent of DKIM authenticated messages delivered to engaged recipients' inboxes that were then marked as spam. The catch: if Gmail already filters much of your mail to spam, fewer people see it in the inbox to report it, so the rate looks low. A low spam rate next to falling clicks is a warning, not good news, and it is where our email deliverability management starts.

Bounce rate

Hard bounces are permanent, like an address that no longer exists. Soft bounces are temporary, like a full mailbox. Mailchimp, for example, removes hard bounces right away and converts an address to a hard bounce after 7 soft bounces, or 15 if the contact has engaged before. A rising bounce rate usually means old addresses, a bad import or an unvalidated signup form.

List growth rate

Many guides subtract only unsubscribes, which flatters the result, so we subtract complaints and hard bounces too. With made up numbers: start at 20,000, add 600 subscribers, lose 150 to unsubscribes, 10 to complaints and 240 to hard bounces. Net growth is 200, or 1.0% for the month.

How to measure email marketing: set up tracking first

Do these six things before trusting any revenue number.

1. Write the goal and KPI into the brief before anyone writes a subject line.
2. Connect your store, CRM or booking system to the email platform so orders flow back.
3. Tag every link with UTM parameters. Google Analytics reads utm_source, utm_medium and utm_campaign, with email as an example medium. It is the only way to see results outside the email platform, like app activity after an activation email.
4. Choose an attribution window and keep it. Klaviyo's 5 day default suits a weekend sale. A long stay RV offer or B2B software decision may need longer.
5. Turn on Apple open and bot filtering where available, and note the date.
6. Benchmark against yourself. The median of your last three months of campaigns is the bar to clear. Published averages mix different lists, platforms and definitions.

What should a monthly email marketing report include?

A useful report answers three questions in plain English: what did email earn, is the list healthy, and what changes next month. Our $1,000 a month email marketing plan includes one plain English performance report every month, and this structure answers all three.

Notice what is missing: a big open rate chart. Keep opens in the report, labeled as directional, because a sudden collapse can flag a deliverability problem, but never judge copy on them. In our monthly email marketing process, the report arrives in the first days of each month, along with the next tests to run.

Which email measurement mistakes should you avoid?

• Comparing open rates across a platform switch or the day you turned on filtering.
• Calling a campaign a winner on clicks without checking whether those clicks bought anything.
• Adding email attributed revenue to ad attributed revenue, when the same order can be counted by both.
• Judging a snowbird offer, like the winter sites email we wrote for Lake Buchanan RV Resort, on the same short window as a flash sale, when winter guests often plan further ahead.

Want a second opinion on your own numbers? Our free email marketing audit reviews your list health, deliverability records and recent campaigns, with no cost and no obligation.

Frequently asked questions