Your Mailchimp open rate is inflated. Here's what to track instead

A newsletter goes out, the Mailchimp report says 42% opened it, and the number goes into the weekly update as good news. Then revenue from that send is flat, and nobody can explain why a campaign that “did so well” sold nothing. The usual explanation is that the open rate was never 42%. A large share of those opens happened on servers, before any person could have read a word.

This post is about what inflates opens, what Mailchimp does with them, what the number still tells you, and what to put on a report instead. It ends with what all this changes about cleaning your list, because the same bad signal that flatters a campaign also decides who you call “inactive”.

Where the extra opens come from

An open is recorded when the mail app loads a tiny invisible image, the tracking pixel, from the sender's server. That used to be a decent proxy for “a person looked at this”. Three things broke it.

Apple Mail Privacy Protection

Since iOS 15 in 2021, Apple Mail users can turn on Mail Privacy Protection, and most do, because it is the default suggestion. Apple then fetches every image in every incoming email through its own servers, whether the person ever opens the message or not. To your sending platform, each of those fetches is an open. Litmus, which tracks email client market share from more than a billion opens, estimates that Apple's feature now touches roughly 55 to 60% of all opens. Omeda measured the effect on about 80,000 accounts and two billion emails: total open rate went from 22.6% to 40.5% in six months, while clicks did not move at all. The audience had not changed. The measurement had.

Gmail's image proxy

Gmail also loads images through its own servers and caches them. The effect is the opposite in one way and the same in another: a person who re-reads an email three times registers one open, and the open carries Google's address and device, not theirs. Opens from Gmail are closer to real than Apple's, but they tell you nothing about where or on what the person read.

Security scanners on business mailboxes

Corporate mail goes through filters such as Microsoft Defender Safe Links, Mimecast and Proofpoint. They open the message and follow every link to check it is safe, seconds after delivery. That registers as an open and as a click, sometimes on every link in the email, including the unsubscribe. If your list has a lot of company addresses, your click rate is inflated too, which is why the rest of this post does not simply say “use clicks instead”.

What Mailchimp does with those opens

Mailchimp counts every pixel load and reports it as an open. Its own Apple MPP FAQ is candid about the consequences, and they go further than the open rate on the campaign report:

• Clicks per unique open looks lower than it is, because the denominator is padded with machine opens.
• Resend to non-openers skips every Apple Mail contact with MPP on, because to Mailchimp they all opened. Mailchimp suggests resending to “didn't click” instead.
• A/B tests decided by open rate pick a winner on noise. Test on clicks.
• Automations triggered by an open fire for far more people than intended, and “did not open” triggers for far fewer.
• Contact ratings (the stars next to each contact) run high for Apple Mail users, since they are built partly on opens.
• Location and email client reports are wrong for those contacts, because the fetch comes from Apple, not from them.

One thing worth switching on: for emails sent after June 22, 2024, Mailchimp can exclude Apple MPP opens from the marketing dashboard and from custom reports. It is a checkbox, it is off by default, and it does not change the per-campaign report. Turn it on and the open rate on your dashboard drops to something closer to the truth. Expect a shock the first time.

What open rate still tells you

Open rate is not useless. It is useless as a score. An email marketer on a recent r/Emailmarketing thread put it in a way that stuck with us: opens are the climate, clicks are the weather. The climate still matters, in three specific ways.

1. A sudden drop is real. Machines open everything, consistently. If your open rate falls from 40% to 25% between two sends to the same list, machines did not stop; your email stopped reaching the inbox. That is a placement problem, and open rate is often the first place it shows.
2. Comparisons on the same list still work. The inflation is roughly constant for a given audience, because the share of Apple Mail users does not change week to week. Subject line A at 44% against subject line B at 38%, on the same list and the same day, is still a difference, just a smaller one than it looks.
3. A rise means nothing. This is the asymmetry to internalise. Opens going up with clicks and revenue flat is not a win. It is usually more Apple Mail users on the list, or more corporate addresses with scanners.

Is 40% a good open rate?

It depends almost entirely on what share of your list reads on Apple Mail, which Mailchimp shows under audience stats. The UK Data & Marketing Association's 2025 benchmark puts the average open rate at 35.9% and the average unique click rate at 2.3%. The first number has been climbing every year since 2021 for no reason other than Apple. The second is the one that reflects behaviour. If someone asks whether your open rate is good, the honest answer is that a 40% on a consumer list is average and means little, and a 40% on a B2B list with no Apple Mail users would be remarkable. The question they want answered is the next section.

What to report instead

Clicks, conversions and revenue are the three that settle an argument. Clicks are directional, conversions are the verdict, and revenue per email is the version of the verdict that a client or a finance person understands without a footnote.

Cleaning the bots out of your clicks

Because clicks are now the headline, it is worth knowing what a scanner click looks like. Mailchimp does not filter them for you, but the click report and a spreadsheet will. The tells:

• A click within seconds of delivery, before the email could have been read.
• A click with no open from the same address, or opens and clicks in the same second.
• Every link in the email clicked, in order, including the unsubscribe and the footer.
• Many addresses at the same company domain “clicking” at the same minute.

You cannot stop these, but you can stop counting them. A click that leads to a page view with time on page, a scroll, a second click or a purchase is a person. A click that leads nowhere is probably a machine. If your analytics can separate the two, report the first.

Reporting it to someone who wants the open rate

This is the part most people in that thread had not solved. The boss or the client asks how email is doing, they have heard of open rate, and a caveat about attribution is the first thing cut from the slide. What works, in our experience, is not to hide the number but to demote it:

1. Lead with revenue per email and conversions, with last week and the same week last year next to them.
2. Show click rate as the engagement line. One number, one trend arrow.
3. Keep open rate on the report, in grey, below the fold, with a single fixed footnote: “Includes automatic opens from Apple Mail and security filters. Useful for spotting drops, not as a score.” Say it once, the same way, every week. After a month nobody argues.
4. If a drop appears, lead with it, because that is the one time open rate is the most important number on the page.

What this changes about cleaning your list

The same signal that flatters a campaign also decides who gets archived. If “inactive” means “has not opened in six months”, the rule is wrong in both directions: every Apple Mail user looks active forever, and every person whose mail app blocks images looks dead while they read and buy. We have seen lists where the “dead” segment kept converting for exactly this reason.

So define inactive by clicks and purchases, with a window that matches how often you send, and sunset in stages rather than in one cut. That is how acadion's audit is set up by default: the rule is “no clicks in 180 days”, opens are off unless you turn them on, and when they are on, the report says plainly that opens are inflated and that the audit errs on the side of keeping contacts. The number of truly inactive contacts is probably higher than it shows. We would rather tell you that than archive someone who was reading all along.

If you want to see what that looks like on your own audience, with your rules and no changes made, run a free audit. It reads your Mailchimp account, scores every contact on clicks and orders, and shows you who your list would lose and what you would stop paying for.