What Is the Most Important Metric in Email Marketing? (It’s Not What You Think)

I still remember the moment everything clicked. It was 2017, and I was sitting in my manager’s office at the digital agency where I cut my teeth. I had just finished presenting a campaign with a 48% open rate. I was feeling pretty good about myself.

Then she pulled up the revenue report. Zero conversions. Not a single sale.

“Ryan,” she said, “what’s the most important metric in email marketing? Because it’s not the one you’re celebrating.”

That conversation changed how I think about email marketing forever. And if you’re still obsessing over open rates, this article might change things for you too.

The Short Answer: Conversion Rate (But Context Matters)

Let me cut straight to it: conversion rate is the most important email marketing metric for most businesses. It’s the number that ties your campaigns directly to business outcomes.

But here’s where most “definitive guides” get it wrong. They give you a single answer and move on. The truth is messier. The most important metric depends on what you’re trying to accomplish.

Launching a brand awareness campaign? Conversions might not be your north star. Running a flash sale? Revenue per email becomes critical. Building your list? Growth rate matters most.

That said, if you forced me to pick one metric that separates successful email marketers from the rest, it’s conversion rate. Here’s why.

Why Most Marketers Track the Wrong Metrics

Here’s a stat that keeps me up at night: 42.7% of marketers still believe open rate is the most important email metric. Another 42.1% say it’s click-through rate.

Only 26% prioritize conversion rate. And just 21.8% track revenue from email as their primary metric.

We’re measuring the appetizers and ignoring the main course.

The Vanity Metrics Trap

I’ve watched smart marketers fall into this trap for years. Open rates and clicks feel good. They’re easy to track. Your ESP shows them right there on the dashboard.

But here’s what those numbers actually tell you: someone might have seen your email. Someone clicked something.

That’s it. That’s all you know.

Vanity metrics look nice in reports but don’t show campaign impact on your bottom line. You can have a 60% open rate and still lose money on a campaign. I’ve seen it happen. I’ve made it happen, back when I didn’t know better.

For a deeper dive into the pitfalls, check out these common email marketing mistakes that trip up even experienced marketers.

How Apple Mail Privacy Protection Changed Everything

If you’re still putting faith in open rates, I need to tell you something: those numbers have been unreliable since September 2021.

That’s when Apple rolled out Mail Privacy Protection. It pre-fetches email content and images for all Apple Mail users. Which means emails get marked as “opened” even when nobody actually reads them.

This affects about 46% of all email clients. Nearly half.

So when you see that 43% average open rate (the 2025 benchmark), understand that it’s artificially inflated. The real engagement is lower. And you have no way to know how much lower.

If you want to understand what’s actually happening with your opens, here’s my guide on how to track email open rates in this new privacy-first world.

Understanding the Email Marketing Metrics Hierarchy

After years of obsessing over this stuff, I’ve developed a simple framework. Think of email metrics as a three-tier pyramid.

Each tier builds on the one below. You can’t have conversions without engagement. You can’t have engagement without delivery. Simple as that.

Foundation Metrics (Deliverability and List Health)

None of your other metrics matter if your emails don’t reach inboxes. Period.

Delivery rate is where everything starts. If you’re seeing delivery rates below 95%, stop worrying about open rates. Fix your foundation first.

I’ve worked with clients who were scratching their heads over poor engagement, only to discover 15% of their emails were bouncing or hitting spam folders. All that content work, wasted.

Need help here? My guide on how to improve your email deliverability covers the technical and strategic fixes.

Engagement Metrics (Opens, Clicks, CTOR)

Once you’re landing in inboxes, engagement metrics help you diagnose what’s working.

• Open rate: Measures subject line effectiveness (with the MPP caveats above)
• Click-through rate: Shows if your content drives action
• Click-to-open rate (CTOR): The truest measure of content quality

That last one deserves attention. CTOR tells you: of the people who opened, how many clicked? It strips out subject line performance and shows you pure content effectiveness.

A healthy CTOR sits between 10-15%. Below that, your email content needs work.

Business Outcome Metrics (Conversions, Revenue, ROI)

This is where the magic happens. The top of the pyramid is where email marketing proves its value.

Conversion rate. Revenue per email. Return on investment.

According to comprehensive ROI data from Litmus, email marketing averages $36 return for every $1 spent. That’s 3,500% ROI.

But here’s the thing: you only capture that value if you’re measuring it. And most marketers aren’t.

Conversion Rate: The Metric That Actually Matters

So let’s talk about the metric that separates email marketers from email senders: conversion rate.

What Counts as a Conversion?

A conversion is whatever action you want subscribers to take. It’s that simple.

For an ecommerce brand, it might be a purchase. For a SaaS company, a trial signup. For a B2B consultant like me, it could be booking a discovery call. For a nonprofit, a donation.

The key is defining your conversion before you hit send. Not after.

How to Calculate Email Conversion Rate

The formula is straightforward:

Some marketers calculate based on total sent or total clicked. I prefer using delivered emails as the denominator. It gives you a cleaner picture of actual performance.

Industry Benchmarks for Email Conversions

What’s a good conversion rate? The 2025 average sits between 2.6% and 3.3%, depending on industry.

Retail and fashion brands tend toward the higher end. B2B and professional services often run lower, but with higher average order values.

If you’re below 1%, something’s broken. If you’re above 5%, you’re doing something right. Keep doing it.

Revenue Per Email (RPE): The Ultimate ROI Metric

For ecommerce brands and anyone selling products through email, there’s an even more powerful metric: revenue per email (RPE).

The calculation is simple: Total Revenue ÷ Emails Delivered.

This number combines your conversion rate with your average order value. It tells you exactly how much money each email generates.

Here’s a benchmark that might surprise you: healthy ecommerce brands generate 20-35% of total revenue from email marketing. During Q4 and holiday seasons, that can spike to 50-60%.

If email isn’t driving at least 20% of your revenue, you’re leaving money on the table. Check out these ecommerce email marketing tactics to close that gap.

The email marketing ROI statistics are clear: 18% of companies achieve ROI greater than $70 for every $1 invested. That’s the potential when you focus on the right metrics.

Other Important Metrics You Should Track (And When They Matter)

Conversion rate is king, but it doesn’t work alone. Here are the supporting players.

Click-to-Open Rate (CTOR): The True Engagement Metric

I mentioned CTOR earlier, but it deserves its own spotlight. This metric answers one crucial question: Is your email content compelling enough to drive clicks?

While open rates are polluted by privacy changes, CTOR remains reliable. A 10-15% CTOR means your content resonates. Below that, you need to work on your copy, design, or offer.

According to academic research on email opening effectiveness, engagement patterns reveal far more about subscriber intent than simple open tracking ever could.

Want to boost that CTOR? Learn how to optimize your email components for maximum engagement.

Deliverability and Bounce Rate: Foundation Metrics

Your bounce rate should stay under 2%. Anything higher signals list hygiene problems or technical issues with your sending infrastructure.

Soft bounces happen. Hard bounces are a warning sign. Too many of either, and ISPs start treating you like a spammer.

Unsubscribe Rate: List Health Indicator

A healthy unsubscribe rate sits under 0.5% per campaign. Higher than that, and you’re either targeting the wrong people or sending content they don’t want.

Some marketers panic over unsubscribes. I don’t. People who unsubscribe are doing you a favor. They’re self-selecting out of a list they don’t belong on. Better that than marking you as spam.

How to Start Tracking What Actually Matters

Knowing conversion rate is important is one thing. Actually tracking it is another. Here’s how to set yourself up for success.

Setting Up Conversion Tracking

Start with UTM parameters. Every link in every email should include source, medium, and campaign tags. This lets Google Analytics (or your analytics tool of choice) attribute conversions correctly.

Next, connect your email platform to your conversion source. Most ESPs integrate directly with Shopify, WooCommerce, and major CRMs. Set it up once and forget about it.

Creating a Metrics Dashboard

Don’t check every metric for every campaign. Build a simple dashboard that shows you what matters:

1. Delivery rate: Did emails reach inboxes?
2. CTOR: Did content resonate?
3. Conversion rate: Did people take action?
4. Revenue/RPE: What’s the business impact?

That’s it. Four numbers that tell you everything you need to know.

Moving Beyond Vanity Metrics

The hardest part isn’t technical. It’s psychological.

We’ve been trained to celebrate big open rate numbers. Breaking that habit takes intention. Start by changing how you report results. Lead with conversions and revenue. Mention opens and clicks only as supporting context.

As strategic persuasion research from SMU and Vanderbilt shows, email’s true power lies in driving specific behaviors, not just catching attention.

The Bottom Line: Match Metrics to Your Goals

Here’s what I’ve learned after years of sending emails and analyzing results: the most important metric is the one that drives your decisions.

For most businesses, that’s conversion rate. It ties directly to revenue and proves email’s value to your organization.

But don’t ignore context:

• Sales campaigns: Prioritize conversion rate and revenue per email
• Awareness campaigns: Focus on reach and click-to-open rate
• Engagement campaigns: Track CTOR and click rate
• List building: Measure growth rate and new subscriber quality

The metric that proves your emails create real business value is the metric that matters. Everything else is just noise.

I think back to that agency conversation with my manager. She wasn’t telling me open rates don’t matter. She was teaching me that they only matter in service of something bigger.

Start measuring what actually matters. Your campaigns (and your revenue) will thank you.

What to Read Next

Ready to put these insights into action? Explore these proven email marketing strategies that directly impact your conversion metrics. And if you’re still wrestling with poor results, don’t miss my breakdown of the common email marketing mistakes that tank performance.

Got questions about tracking your own metrics? I’d love to hear what’s working for you and where you’re stuck.