How Sergio grew his platform for newsletter creators to 1k registered users

Meet Sergio Pulido.

Sergio is from Spain. He founded his first company almost a decade ago (2015’ish) and hasn’t stopped building since.

He has created projects as different as an online English academy (sold), a digital advertising agency (sold), and most recently a platform for newsletter creators called LetterBucket (the focus of this story).

Today Sergio is fully focused on the creator economy. A movement that, as he puts it, is completely transforming the way people get informed, learn, and connect.

“Individual creators are now capturing more attention, trust, and credibility than traditional media. It’s a massive wave… and it’s worth surfing.”, Pulido says.

LetterBucket was born right at that intersection, where technology meets creative independence. Sergio’s goal isn’t to build the biggest platform, but the simplest one.

The story told by Sergio Pulido

The vision

Before building LetterBucket, I spent several years working side by side with all kinds of content creators, writers, financial analysts, speech therapists, teachers… people with so much to share, but without the right tools to do it. During that time, I kept hearing the same complaint: “I want to make a living from my knowledge, but every platform just makes things harder.”

I remember, for example, an economist who wanted to send his market insights to his audience every week. He ended up spending more time configuring domains and templates than actually writing. Or a language teacher who wanted to share her lessons by email, but got lost among integrations, embed codes, and analytics dashboards that made no sense.

That’s when it became crystal clear to me: sending a newsletter had become way harder than it should be.

Setting up DNS, connecting forms, customizing templates, interpreting metrics… it had all turned into a trap for people who simply wanted to write and reach their audience.

That’s how LetterBucket was born. Not as a grand idea, but as a reaction to unnecessary complexity.

Day one: A minimal product and a lot of drive

We started coding LetterBucket in September 2024 and honestly it turned out to be a bigger challenge than we expected. The plan was to launch a super lean MVP, but we were stepping into an industry that has been solid for years.

You can’t show up to the prom in shorts and a ripped shirt. People notice!

So we had to polish the product a lot, bring in early users little by little, listen to everything they said and keep raising the quality until it felt right.

We started with one clear idea: if creating a newsletter takes more than five minutes, something’s wrong. So we focused on building only what truly mattered. A clean editor, a distraction-free interface, and instant setup.

We didn’t want to be another platform with a thousand buttons. We wanted someone to open LetterBucket, write, hit send, and forget about the rest.

We did our official public launch on June 25.

During the first few weeks, the product was so bare-bones it was almost embarrassing. But it worked. And the best part was that people understood it instantly. That was our first big lesson: when something is genuinely simple, it doesn’t need an explanation.

The first users: Conversations, not campaigns

Starting out we didn’t run ads. There was no budget and honestly, no reason to. Instead, I decided to write personally to creators I already admired. I sent them a short, honest message:

“Hey, I’m building a newsletter platform. It’s simple, distraction-free, and free up to 1,000 subscribers. It might actually fit you better than what you’re using now.”

That’s how the first users arrived. Some came from Substack, others from Beehiiv or Kit.

Many stayed mostly for one reason: they felt heard. Every piece of feedback became an improvement. Every suggestion turned into a discussion. LetterBucket literally grew one conversation at a time.

More marketing

Early-stage attribution was… painful. We tried a lot of guerrilla stuff and collected plenty of bans along the way. Some things worked, some didn’t, so here’s the honest breakdown.

Affiliates

We launched a very aggressive referral program. For a couple of months it worked great, but it turned out to be more expensive than other channels. We were giving 60% for 12 months which is objectively insane. Still, it helped us get early volume fast, so no regrets.

Reddit

We’ve been Redditors forever and yes, the platform has gone downhill since going public, but it’s still a goldmine for learning and conversations.

We joined every newsletter thread we could find and at one point someone posted about LetterBucket in a huge subreddit. The spike in traffic was so wild we didn’t even make the connection until the post got deleted by moderators.

LinkedIn

Mixed feelings.

We’ve had good leads and solid conversations, but as a channel it’s not something we’re prioritizing now. It’s a bit too slow for the stage we’re in.

Newsletters

This one will shock absolutely no one.

We reached out to newsletters we thought were a good fit for ads, and it worked surprisingly well from day one. I’d call this one of the key drivers because the users coming through newsletters are now referring others.

Referrals

This is the main channel and the one that consistently performs.

Nothing beats your friend telling you “Hey, use this, it actually works”. I wish we could double down on this one even more.

How we’re different

From day one, we were very clear about what we didn’t want to be:

• A bloated suite packed with unnecessary options.

• A pricing model that punished growth.

• A tool only people with marketing backgrounds could actually use.

And what we did want was simple:

• A clean, intuitive design that anyone could understand.

• The ability to send a newsletter in under five minutes.

• To listen to creators and deliver real value week after week.

The business model

The business model is pretty simple and it comes from two places.

The first one is the classic mailing SaaS model. You pay a monthly fee based on how many subscribers you have. Our biggest cost is sending emails at scale, so that fee covers the sending costs and leaves us a margin to run the company.

The second stream, which isn’t live yet, will come from advertising. Sponsors will be able to promote their products inside newsletters that choose to run ads. We handle the workflow and take a small commission.

We had a few ideas for add ons and other fancy monetization tricks, but in the end it only adds complexity and doesn’t match what we want to build. Our goal is to give users a tool that makes their newsletter genuinely better and charge a clear flat fee for it.

The Mistakes (because there were plenty)

I could say everything was part of the plan, but that would be a lie.

Along the way, we tested ideas that simply didn’t work. We focused on ICPs (Ideal Customer Profiles) that didn’t really align with us, built automations that looked clever but lacked soul, and even spent nearly two months developing two integrations… that no one ever used.

But each misstep strengthened something more valuable than any feature: judgment.

Build slow, but build right.

We also learned that the biggest threat to a good product isn’t competition, it’s impatience. When you get obsessed with shipping faster or trying to impress everyone, you stop listening to the users who already trust you.

One of the toughest mistakes we made was purely technical. We onboarded two creators with large audiences (tens of thousands of subscribers) far too early, before our IPs were properly warmed up for that kind of sending volume. The result: emails landing in spam folders or getting blocked by Gmail and Outlook filters.

We had to learn the hard way what proper IP warm-up really means, how to manage domain reputation, how SendGrid rate limits behave under heavy load, and how to interpret delivery and bounce events to protect the overall deliverability of the platform.

We also ran into bugs that only appear in production: duplicate webhook events, false opens triggered by Apple and Google proxy crawlers, and automations inflating metrics in unpredictable ways.

Each technical failure became a product lesson. Understanding that scaling isn’t growth; it’s surviving without breaking.

Today, we know that a great SaaS isn’t the one that ships the fastest, it’s the one that can send a million emails and still remain reliable, stable, and trusted.

The numbers

Since we’re always in conversations with VCs I’m a bit limited on what I can share, but I can give some numbers that don’t break any NDA.

We’re close to hitting 1k registered users (around 200 active). Altogether, they reach over a million subscribers, and we send millions of emails every month.

Each user can run up to two newsletters (most run one) so the total number of newsletters on the platform is higher than 200. Activity varies (some send just one post a month), but roughly 200 newsletters are actively publishing.

If you want a good proxy of real usage, here’s the honest one. If we push an update and something breaks, we get a wave of messages in the chat and in the inbox within the first couple of hours. That’s when you know people are really using the product.

Btw, it’s the perfect moment to say sorry to all of them publicly and thank them for their patience whenever things go wrong! They’ve been incredibly supportive while we keep moving fast and pushing updates.

Most of our traffic comes from the USA, which is exactly what we expected. After that it’s Canada and the UK. Spain held the fourth spot for a while but it just got overtaken by… Singapore.

Fun fact. We onboarded a big creator from Singapore and with his first couple of sends he instantly pushed the country ahead of almost everyone else. It was a funny spike to watch in real time.

What we learned along the way

If I had to sum up what this project has taught us:

• There’s no growth without simplicity. Removing is just as important as adding.

• Direct feedback is worth more than any metric.

• Building a product isn’t about launching an app, it’s about building trust.

Looking ahead

Today, LetterBucket has a solid foundation and a community that grows every day.

We’re still obsessed with the same goal to be the most useful platform for creators. Yes, we keep adding new features, but under one simple rule:

“If it doesn’t improve the creator’s experience, it doesn’t make it in.”

My goal with LetterBucket is to build a space where creators can write without worrying about the technical side where they don’t need to be marketers to grow, or developers to edit.

A tool that simply works.

The team

I’ve been building things with my brother and a close friend since the beginning. We were all obsessed with the internet, tech, and business when we were kids, so teaming up and launching projects together felt completely natural.

Over the years the team has grown. Right now we have five people working for us full time. Still very much a pizza-size team, which means everything moves fast and there are zero bottlenecks.

Connect with Sergio Pulido

• LinkedIn

• letterbucket.com

See you next time,
Thanks,
Jakob Jelling

I’m on X. Come out and play.