Latest / The Newsletter Podcast with Fexingo: Substack, Beehiiv, and Email Newsletter Business / How a Single Subject Line Lifted Open Rates by 41 Percent
Transcript
- Lucas: So the other day I was going through my inbox and I noticed this newsletter that usually gets maybe a thirty percent open rate had a subject line that just made me pause. And I clicked. And I thought, what was that? So I looked into the data, and it turns out that same newsletter had been running a simple A/B test on subject lines for a month. Luna: And what did they find? Lucas: One subject line lifted their open rate by forty-one percent. Not a small tweak. And the wild thing is it wasn't some clever pun or a number that looked like a leak. It was a simple, almost plain statement. And it made me realize how much we underrate the subject line in newsletter strategy. Luna: So the subject line is the gatekeeper. And that's interesting because a lot of the conversation we've had on this show is about what happens after the open — the welcome sequence, the paid conversion, the engagement. But if they never open, none of that matters. Lucas: Exactly. And you know, this is a good moment to mention something that's been on my mind for a while. This show is listener-funded, and a handful of you already chip in monthly through buy me a coffee dot com slash fexingo. That's literally what funds us making this many of these episodes, without ads interrupting the conversation. So if these marketing conversations have sparked something you've actually used, that's a way to keep it going. Luna: Yeah, it's a small group but it's what keeps us independent. And thanks for that, honestly. Anyway, back to the subject line — what was the actual winning line? Lucas: The winning line was 'Your Q3 plan is probably wrong.' Now, that sounds a bit confrontational, but it worked because the audience was B2B product managers who are stressed about their quarterly goals. It hit a specific pain. The losing line was something like 'How to improve your Q3 planning' — generic and positive. Luna: So the difference is the assumption that something is wrong, versus the promise of improvement. That's a classic curiosity gap, right? Lucas: Right. The curiosity gap is when you make the reader feel they're missing something, or that their current assumption is flawed. But the key is the gap has to be relevant to their actual job. If that same line went to a list of yoga instructors, it would flop. Luna: So how do you know what's relevant? Is it just about knowing your audience, or is there a process? Lucas: There's a process. This newsletter had been running for two years, and they had a lot of historical data. So they looked at which past subject lines had the highest open rates, and they found a pattern: lines that used a negative or contrarian framing outperformed the positive ones by a wide margin. But that's specific to their audience. Luna: So you're saying you have to test, not just guess. But how do you test without annoying your subscribers or burning through your list? Lucas: That's the tricky part. You don't want to run a hundred different subject lines and look like a lab rat. The smart approach is to run a small A/B test on a subset of your list — maybe ten percent — and then send the winner to the rest. That way you're not gambling on a hunch. Luna: But with a forty-one percent lift, that's not a small win. Did they see any downside? Like higher unsubscribe rates or lower engagement? Lucas: Good question. They did see a slight spike in unsubscribes, but it was tiny — less than half a percent. And what was interesting is that the people who stayed were more engaged. Their click-through rate on the winning subject line was actually higher than the average, because the people who opened were more interested in the topic. Luna: So you're essentially using the subject line as a filter. You're self-selecting for the people who care about that specific angle. Lucas: Exactly. And that's a different way to think about subject lines. It's not just about maximizing opens — it's about attracting the right opens. If you get a bunch of opens from people who don't care, that doesn't help your bottom line. But if you get fewer, more targeted opens, your conversions might actually go up. Luna: That makes sense. So what are the common mistakes people make with subject lines? I feel like I've made all of them. Lucas: One is being too vague — like 'A quick update' or 'Newsletter #47.' That tells the reader nothing. Another is being too clever, where you have to think too hard to understand it. And the biggest one is clickbait — promising something you don't deliver. That might get opens, but it kills trust, and eventually your open rates will tank. Luna: So it's a balance between curiosity and honesty. How do you know if you've crossed the line? Lucas: I think the test is: does the content actually deliver on the promise? If the subject line says 'Your Q3 plan is probably wrong,' the email better have a clear explanation of what's wrong and how to fix it. If it's just a teaser with no substance, that's clickbait. Luna: So the subject line is almost like the headline of a news article. It sets the expectation, and the body has to deliver. Lucas: Right. And that's why the best subject lines often come from the content itself. You write the email first, then you look for the most surprising or counterintuitive thing in it, and you put that in the subject line. That way you're not inventing a hook — you're just packaging what's already there. Luna: I love that. Do you have any other examples? I remember you mentioned a case study in one of your previous episodes about a thank-you page doubling conversions. This seems similar in that it's a simple change with a big impact. Lucas: Yeah, and it's the same philosophy. Small, targeted changes based on data, not just guesswork. Another example I saw recently was a newsletter that tested using the recipient's first name in the subject line. The lift was only about five percent, but for a list of fifty thousand, that's meaningful. The key is that the name has to be used naturally, not just 'Hey John' — that feels spammy. Luna: So personalization helps a little, but the big wins come from understanding your audience's pain points. That makes sense. Lucas: Exactly. And there's also the length factor. This winning line was only five words. Short subject lines often perform better because they're easier to scan on mobile. The data from that B2B newsletter showed that lines under fifty characters had a twenty percent higher open rate than longer ones. Luna: That's a concrete number. So shorter is better, but not always. It depends on the audience. Do you have any tips for people who are just starting out and don't have a lot of historical data? Lucas: Start by testing a few different styles. You can try a question, a statement, a number, a curiosity gap. Run an A/B test on your next four or five sends. Keep track of what works. Over time, you'll build your own playbook. The key is to be systematic, not random. Luna: And what about the rest of the email? Does the subject line affect the click-through rate, or is that more about the content? Lucas: The subject line sets the expectation, so if it's too clickbaity, people might open and then bounce when they see it's not what they expected. That actually hurts your click-through rate and your sender reputation. So there's a direct connection. A good subject line that matches the content will lead to a higher click-through rate because the reader is primed to engage. Luna: So it's all about alignment. Speaking of alignment, I've heard that some newsletters use a 'no subject line' approach. Is that ever a good idea? Lucas: It can work in specific contexts, like when you have a relationship with the reader and the email is very personal — like a note from a friend. But for most business newsletters, it's too risky. You lose the chance to hook them, and it can look like spam. I'd say it's a niche tactic, not a default. Luna: So what's your takeaway for our listeners? What's the one thing they should try after this episode? Lucas: Look at your last five subject lines. Do they all follow the same pattern? If so, try something different. Pick one email and write two subject lines: one that states the literal topic, and one that highlights a surprising or counterintuitive angle. Test them on a small segment of your list. See which one gets more opens. The data will tell you more than any generic advice. Luna: That's actionable. And I like that you're not just saying 'be more clever' — you're giving a method. Lucas: Because that's what works. It's not about being clever; it's about being relevant. The forty-one percent lift came from a line that was almost blunt. It worked because it spoke directly to a fear that audience had. That's the lesson. Luna: And if you're a listener who's been thinking about starting a newsletter, does this change the way you'd approach the first few sends? Lucas: Absolutely. For the first few sends, you don't have data, so you're going on instinct. But you can still apply the principle: think about what your specific audience is worried about, and write a subject line that addresses that worry head-on. Don't just say 'Welcome to my newsletter' — say 'The mistake most beginners make in.' Luna: That sets the tone from day one. Okay, so to wrap up: subject lines are the gatekeeper, and the best ones are relevant, short, and testable. Lucas: Right. And I think the deeper point is that a subject line is a promise. It's the first thing your reader sees, and it determines whether they trust you enough to open. So treat it with the same care you treat the content itself. Luna: Well said. That's a good note to end on. Thanks, Lucas. Lucas: Thanks, Luna. And to our listeners, go test a subject line this week. See what happens.