Latest / The Email Marketing Podcast with Fexingo: Newsletters, Open Rates, and Subscriber Growth / How Email List Co-Registration Doubles Growth
Transcript
- Lucas: If you’ve been building an email list for a while, you’ve probably tried lead magnets, pop-ups, maybe a referral program. But there’s a less common tactic that can double your growth rate almost overnight — and it doesn’t require creating any new content. Luna: Okay, I’m intrigued. What’s the tactic? Lucas: It’s called co-registration. The basic idea is you partner with a brand that serves a similar audience to yours, and you offer a joint sign-up. Someone signs up for their newsletter and checks a box to also receive yours — or vice versa. Luna: So it’s like a bundled opt-in. I’ve seen this mostly with travel brands — like booking a flight and being offered a destination guide newsletter. Lucas: Exactly. That’s a great example. I spoke with the founder of a travel newsletter called 'The Weekend Wanderer' — not a huge brand, maybe 40,000 subscribers at the time. They partnered with a luggage company that had a much bigger email list, about 300,000 subscribers. Luna: What was the offer? 'Sign up for luggage deals and get travel tips'? Lucas: Close. The luggage company had a pop-up offering 10 percent off a carry-on in exchange for signing up for their emails. They added a pre-checked box that said 'Yes, send me trip ideas from The Weekend Wanderer.' So you’re already in a buying mindset — you want the discount — and you get this bonus content. Luna: How many new subscribers did the newsletter get from that? Lucas: In six months, they added roughly 12,000 subscribers from that single partnership. That’s about a 30 percent increase in list size. And the quality was surprisingly good. The co-reg cohort had a 34 percent open rate, compared to 28 percent for their organic sign-ups. Luna: That’s interesting — I would have worried that a pre-checked box would bring in low-intent subscribers who just click through for the discount. Lucas: That's the risk. But they managed it with two things: first, the partner brand’s audience was already travel-interested. People buying a carry-on are likely to want destination content. Second, they used a two-step confirmation — after the co-reg checkbox, the subscriber received a separate welcome email asking them to confirm their subscription. That extra click filters out people who really don’t want it. Luna: So it’s a double opt-in, but from a partner source. That makes sense. I imagine the partner also benefits — they’re adding value to their own sign-up flow. Lucas: Exactly. The luggage company saw a slight increase in their own conversion rate because the offer of a bonus newsletter made their sign-up more compelling. So it’s a win-win. And the newsletter didn’t pay anything — they just gave the luggage company a shout-out in one of their emails each month. Luna: That’s a great deal. So co-registration is essentially bartering access to each other’s audiences. Lucas: Right. And it works best when the audiences overlap but aren’t identical. A travel newsletter and a luggage brand — that’s a perfect fit. A finance newsletter and a meal kit service? Less so, unless you’re targeting the same demographic. Luna: What about legal compliance? Under GDPR, pre-checked boxes are not allowed. You have to have an affirmative opt-in. Lucas: That’s a crucial point. In the EU, you cannot use a pre-checked box. The subscriber must actively check it themselves. So for European audiences, the partner would need a blank checkbox, not a pre-ticked one. That slightly lowers conversion, but it’s still effective. And under can spam in the US, pre-checked boxes are generally allowed as long as the disclosure is clear. Luna: So you have to tailor the approach by region. Also, I’d guess the partner’s email list must be permission-based — you can’t co-register with a list that was bought or scraped. Lucas: Absolutely. You need to vet the partner. If they’ve been sending to rented lists or have poor deliverability, that reputation transfers to you. So you want a partner with a clean list and good sender score. The Weekend Wanderer checked the luggage company’s deliverability using a free tool before agreeing. Luna: Smart. Co-registration sounds a bit like list rental, but with a key difference — the subscriber is actively opting in to your list at the point of sign-up, not being passed a file. Lucas: That’s exactly the distinction. In list rental, you buy a list of emails and send to them once. Those people never opted in to hear from you. Co-registration is permission-based because the subscriber chooses to receive your emails right there. So it’s far more compliant and the engagement is higher. Luna: And you’re not paying per email — you’re trading value. I can see why this is underused. Most marketers focus on creating their own lead magnets, but partnerships can be just as powerful. Lucas: And it’s scalable. Once you have one partnership working, you can replicate it with other complementary brands. The Weekend Wanderer went on to partner with a travel insurance company and a language learning app. Each partnership added thousands of subscribers. Luna: I want to try this with my own list now. What’s the best way to approach a potential partner? Lucas: Start with brands that already sell to your audience — think about what your subscribers buy. Then look for companies that have an email list bigger than yours. Reach out to their marketing team with a specific proposal: 'We’ll promote your product to our list in exchange for a co-registration spot in your sign-up flow.' Be clear about the value you’re offering. Luna: Do you recommend starting with a small test? Maybe a week-long co-registration to see how the audience responds? Lucas: Definitely. Run it for two to four weeks. Measure the number of new subscribers, their open rate after 30 days, and the click-through rate. If those metrics are close to your organic sign-ups, you can scale it up. If not, adjust the offer or the placement. Luna: One thing I’ve noticed — these marketing conversations often spark ideas we actually use. And that's part of why we keep this podcast ad-free. We don't run sponsorships or commercials. If you find value in what we share and want to support that choice, you can at buy me a coffee dot com slash fexingo. It's a simple way to help us keep doing this without selling your attention. Lucas: Yeah, we really appreciate that. And it keeps the show focused on what works, not what pays. So back to co-registration — let’s talk about the numbers that make this worthwhile. Lucas: The Weekend Wanderer tracked lifetime value of co-reg subscribers versus organic. After twelve months, the co-reg cohort had a similar purchase rate for their paid travel guides — within 5 percent of organic. So the acquisition cost was essentially zero, and the value was almost identical. Luna: That’s impressive. So it’s not just about volume; it’s about quality. What’s the biggest mistake you see people make with co-registration? Lucas: They choose the wrong partner. I’ve seen newsletters partner with brands that have a completely different audience — like a B2B SaaS newsletter partnering with a pet supply company. The opt-in rate might be high, but engagement tanks because the subscribers don’t actually care about the content. Luna: So relevance is everything. Also, I imagine the placement of the checkbox matters — above the fold, clearly labeled, not buried in fine print. Lucas: Exactly. The best conversion comes when the checkbox is right next to the primary call to action, with a line like 'Also get for free.' You want it to feel like a bonus, not an afterthought. Luna: What about using co-registration to grow a newsletter that’s already large? Does it still move the needle? Lucas: It can, but the partner needs to have a significantly larger list. If you have 100,000 subscribers and partner with a brand that has 50,000, the impact might be modest. But if you partner with a brand that has 500,000, you could see a 10 to 20 percent boost in a few months. It’s all about relative size. Luna: So it’s especially good for smaller newsletters that want to jumpstart growth. Larger lists might need multiple partnerships to see a meaningful effect. Lucas: Right. And you can also layer co-registration with other growth tactics. For example, run a co-registration partnership at the same time as a referral campaign. The referral campaign brings in subscribers who already trust you, and the co-reg brings in subscribers from a trusted partner. They complement each other. Luna: I’ve also seen some newsletters offer a small discount or bonus to the partner’s customers who opt in — like a free chapter of a book. Does that help? Lucas: It can, but you have to be careful not to attract too many incentive-seekers. If the discount is too good, you might get people who sign up just for the deal and then unsubscribe. The travel newsletter I mentioned didn’t offer any extra incentive — just the promise of good content. That kept the quality high. Luna: So the offer itself should be the content, not a bribe. That makes sense. Lucas: Exactly. And finally, don’t forget to track the source. Use a unique UTM parameter or a dedicated sign-up page for each partner. That way you can attribute new subscribers accurately and know which partnerships are worth continuing. Luna: Great advice. I’m going to look into potential partners in my niche this week. Thanks, Lucas. Lucas: Happy to help. Co-registration is one of those tactics that looks simple on paper but takes a bit of relationship-building to execute well. But when it works, it’s a real growth lever.