Email Open Rate
Email MarketingAlso: Open Rate · Email Open Percentage
Quick definition
Email open rate is the percentage of delivered emails that are recorded as opened. Calculated as emails opened divided by emails delivered, expressed as a percentage. Since Apple's Mail Privacy Protection (MPP) launched in 2021, recorded open rates have been inflated for a large share of audiences and are no longer a reliable standalone metric.
How it varies across Australia
Open rates vary sharply across Australian industries, and that variation is genuine. B2B service businesses tend to see higher rates than ecommerce. Transactional emails outperform promotional sends. The more important caveat is that post-MPP, the absolute numbers are inflated by an unknowable margin for any list with a large share of Apple Mail users. Trend matters more than the number itself.
See email performance patterns across Australian industries →What it actually means
Open rate was once the first number everyone checked after a send. It was the heartbeat of an email programme. High open rate meant the subject line worked, the sender reputation was clean, the list was engaged. Low open rate meant something was wrong and you needed to find it.
That picture changed in September 2021 when Apple launched Mail Privacy Protection (MPP). MPP pre-loads email content in the background before a user decides whether to open it. That pre-load registers as an open in your email service provider. For lists with a material share of Apple Mail users, which is most Australian consumer lists, this means a large chunk of your reported opens never happened.
The problem isn't that open rate is now useless. The problem is that it's now noisy in a way that varies by list composition. A B2B list dominated by Outlook users still gives you reasonably clean open rate data. A consumer list with heavy iPhone usage gives you inflated opens you can't trust for day-to-day decisions.
The practical response is to treat open rate as a directional signal, not a performance metric. Use click-through rate (CTR) and click-to-open rate (CTOR) for actual engagement measurement. Use revenue per email and conversion rate for performance measurement. Keep watching open rate as a deliverability signal: a sudden drop is still meaningful even if the absolute number isn't.
Open rate felt like a pulse check. Apple MPP turned it into a blood pressure cuff with a broken gauge.
How to calculate it
Open Rate = Emails opened ÷ Emails delivered × 100
Worked example. You send 8,000 emails. 400 bounce and are excluded, so 7,600 are delivered. Your platform records 1,900 opens. Open Rate = 1,900 ÷ 7,600 × 100 = 25%. Post-MPP, some unknown portion of those 1,900 recorded opens are Apple pre-loads rather than real user opens.
The Australian context
Australian consumer lists skew heavily toward Apple devices, which means MPP inflation is a genuine problem for most Australian marketers running consumer programmes. B2B lists in corporate Australia tend to be heavier on Outlook and Microsoft 365 clients, where MPP isn't a factor, so B2B open rate data remains more reliable.
Australian spam rules under the Spam Act 2003 require consent for commercial emails. This means compliant Australian lists are generally higher-quality than unconsented lists in markets with looser regulations, and that keeps baseline open rates somewhat higher. But compliance does nothing to fix the MPP measurement problem.
Where people get this wrong
Related terms
Common questions
Is email open rate still worth tracking?
Yes, but not as a performance metric. Open rate is still useful as a deliverability signal and for broad subject-line testing. A sudden drop is worth investigating. A gradual rise post-MPP is not necessarily meaningful. Use click-through rate and click-to-open rate for actual engagement decisions.
What did Apple MPP do to open rate data?
Mail Privacy Protection pre-loads email content when it arrives in Apple Mail, which registers as an open before the user decides whether to read it. For lists with a large share of Apple Mail users, this inflates open rates by an amount that varies by list and can't easily be separated out without additional segmentation.
What should I use instead of open rate?
Click-through rate is the more reliable engagement signal. Click-to-open rate (clicks as a share of opens) helps isolate whether the email body is converting interest into action. For revenue-focused programmes, revenue per email sent is the cleanest performance measure.
What is a healthy open rate for an Australian email list?
Post-MPP numbers vary widely and are inflated for consumer lists. B2B programmes in Australia tend to see higher rates than consumer ecommerce. The more useful question is whether your rate is stable or improving over time within your own data, not how it compares against a published benchmark.
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About New Rebellion
New Rebellion is a marketing intelligence consultancy. We build tools, score Australian businesses on how their marketing actually performs, and publish Debrief every day. This dictionary is part of how we work in the open.
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