Latest / The Email Marketing Podcast with Fexingo: Newsletters, Open Rates, and Subscriber Growth / Why Subject Line Personalization Can Backfire
Transcript
- Lucas: So there's this study from the Email Experience Council, released late last year — 2025 — and it found something that feels almost counterintuitive. Emails with personalized subject lines — first name, recent purchase, that kind of thing — actually saw open rates drop by an average of 2.3 percent across the sample. And for some segments, it was worse. Luna: Wait — personalization hurt open rates? That goes against pretty much every best-practice list I've ever seen. Lucas: I know. And look, personalization in the right context still works. But the study zeroed in on one specific failure mode: when the personalization feels forced or irrelevant to the email's purpose. They looked at over 200 million emails from more than 1,200 brands. The worst-performing category was B2B SaaS companies using first-name personalization in cold-ish newsletter content. Luna: Right — because if I get an email from a company I barely remember signing up for, and it starts with 'Hey Luna, here's this week's marketing roundup,' that first name doesn't build trust. It feels like a data grab. Lucas: Exactly. The researchers called it the 'personalization paradox.' When the relationship is weak, personalization actually amplifies the sense of intrusion. They measured it by comparing open rates for the exact same email sent to two groups: one with 'Hey ' in the subject line, one without. The plain subject line outperformed by 4 to 12 percent depending on the audience's level of engagement. Luna: So when does personalization actually help? I'm guessing welcome emails and transactional messages? Lucas: That's exactly where it works. The study found that in triggered emails — abandoned cart, order confirmation, re-engagement — personalization lifted open rates by 6 to 9 percent. Because in those cases, the subscriber expects you to know who they are. It's contextual. But in a broadcast newsletter, the same tactic backfires. Luna: That makes sense. There's a difference between 'I know you because you just did something' and 'I know you because I have your data.' Lucas: Right. And the nuance matters. The researchers also looked at subject line length. Personalized subject lines that were longer than 50 characters saw the biggest drop — over 8 percent lower open rates. Short personalized lines — under 30 characters — performed about the same as non-personalized ones. So if you're going to personalize, keep it tight. Luna: I want to talk about the B2B SaaS example you mentioned earlier. What did that look like in practice? Lucas: Sure. One case they highlighted was a project management tool — think of a company like Asana or Monday.com. They sent a weekly newsletter with tips and product updates. The control group got a subject line like 'This week's top productivity tips.' The variant got 'Hey, check out these tips.' The variant's open rate dropped 12 percent. And the unsubscribe rate went up 3 percent. Luna: That's a meaningful lift in unsubscribes. So the personalization didn't just fail to engage — it actively pushed people away. Lucas: Exactly. The data shows that when personalization feels like a tactic rather than a service, it erodes trust. And trust is hard to rebuild. The Email Experience Council followed up with a survey of 2,000 consumers. 41 percent said they're less likely to open an email from a brand if the subject line uses their first name without a clear reason. Luna: That's a huge number. So what's the alternative? Just never use first names? Lucas: Not never — but be surgical. The study recommends using personalization only when you have a specific, relevant reason. For example, if the email references their recent activity, or if it's a follow-up to a support ticket. Otherwise, focus on relevance through segmentation rather than individualization. Segment by behavior, not by name. Luna: I've been thinking about this in the context of the recent privacy shifts. With iOS 15's Mail Privacy Protection and Google's planned changes, open rates are already less reliable. If personalization can hurt, maybe it's time to rethink what metrics we optimize for. Lucas: That's a great point. The study actually looked at click to open rate as a secondary metric. For the personalized subject lines, click to open rates were also lower — about 3 percent worse on average. So it's not just that fewer people opened; those who did open were less likely to engage. Which suggests the personalization set the wrong expectation. Luna: Like, 'Oh, this email is about me — wait, no, it's the same generic content for everyone.' Lucas: Exactly. The subject line promised something the body didn't deliver. That's a classic bait and switch, even if unintentional. And the data shows subscribers punish that behavior. Luna: So what's the one takeaway for a marketer listening right now? Lucas: I'd say: test your personalization against a plain control. Don't assume it works because it's 'best practice.' And if you're a B2B company sending a newsletter, try removing the first name from your subject line for a month and see what happens. You might be surprised. Luna: I've actually seen this play out with a client. They had a campaign that used 'Hey, your weekly insights are ready' — and when they switched to 'Your weekly insights are ready,' open rates went up about 7 percent. It was a small sample, but the direction was clear. Lucas: That's exactly the kind of data more marketers need to see. And it ties into something bigger: the idea that personalization should be earned, not assumed. If the relationship isn't there yet, a simple, relevant subject line outperforms a personal one every time. Luna: You know, conversations like this — where we dig into real data and challenge common assumptions — are exactly why I love this show. And it's also why listener support matters so much. If you find these marketing deep dives useful, you can help keep the show ad-free by buying us a coffee at buy me a coffee dot com slash fexingo. It's a small gesture that goes a long way. Lucas: Yeah, we really appreciate that. It helps us keep doing episodes like this one — where we can spend time on a single study and really unpack it. So thank you to anyone who's contributed. Luna: Alright, back to the data. Lucas, you mentioned the 41 percent of consumers who are less likely to open a personalized subject line. That's a pretty damning stat. How should marketers reconcile that with the fact that some personalization still works? Lucas: I think the key is context and frequency. If you only personalize occasionally — say, on a birthday email or after a purchase — it feels thoughtful. But if every single email has 'Hey,' it becomes noise. The study found that brands that personalized less than 20 percent of their emails saw better results from those personalized emails than brands that personalized more than 60 percent. Luna: So scarcity makes personalization more effective. That's a good rule of thumb. Lucas: Exactly. And there's another layer: the type of personalization. Using a first name is the most common, but it's also the most likely to feel superficial. The study found that personalization based on recent behavior — like 'Your cart is waiting' or 'We saved your progress' — performed much better than name-based subject lines. Those behavioral triggers had open rates 8 to 15 percent higher than the control. Luna: So it's not personalization per se that's the problem — it's the type and the frequency. Behavioral personalization feels helpful. Name-only personalization can feel like a trick. Lucas: Right. And the research also looked at demographics. Younger audiences — 18 to 34 — were more tolerant of name personalization, with only a 1 percent drop in open rates. But for audiences over 55, the drop was over 5 percent. So age matters too. Luna: That aligns with what we know about privacy sensitivity. Older demographics tend to be more protective of their data. Lucas: It does. And it reinforces the idea that one-size-fits-all personalization is a mistake. The best approach is to segment your list by engagement level and lifecycle stage, then test personalization within each segment. Luna: So what's the next step for someone who wants to audit their own subject line strategy? Lucas: I'd start by pulling your last 90 days of email performance. Look at every campaign that used a personalized subject line. Compare the open rate and click to open rate against a non-personalized control. If you don't have a control, set up an A/B test on your next send. Just 50-50 split, half with personalization, half without. Run it for a week and see what the data says. Luna: That's actionable. And I'd add: don't just look at opens. Look at unsubscribes and spam complaints too. Those are the real signals of trust erosion. Lucas: Great point. The Email Experience Council found that personalized subject lines increased spam complaint rates by 0.2 percent on average. That might sound small, but it compounds. Over a year, a 0.2 percent monthly increase can hurt your sender reputation significantly. Luna: Alright, so let's wrap with a framework. When should you use personalization, and when should you avoid it? Lucas: Use it when: the email is triggered by a specific user action, the relationship is established, and the personalization goes beyond just a name — reference their behavior or preferences. Avoid it when: the email is a broadcast newsletter, the subscriber hasn't engaged recently, or you're reaching out for the first time. And always test. Luna: That's a solid heuristic. And it's refreshing to hear a nuanced take on personalization — it's not about abandoning it, but about using it intelligently. Lucas: Exactly. The data is clear: subscribers are smarter than we give them credit for. They know when personalization is genuine and when it's just a script. Our job is to earn that trust.