Zeno Rocha

Resend

Resend: Open Source First to $5M ARR with a 22-Person Team

$25M ARR

Current revenue · as of December 2025

Zeno Rocha (founder)

1 year

$10K MRR

Twitter / X

Growth channel

Co-founders

Founder

Zeno Rocha

Co-founders•Technical•USA

Commitment

Full-time

Experience

Experienced

Product

Resend

Email API for developers that makes sending transactional and marketing emails as simple as Stripe made payments, with React-based email templating.

Type

API / developer tool

Industry

Developer tools

Model

Freemium

Marketing strategy

How Zeno acquired customers

Growth channel

Twitter / X

Also used

CommunitiesProduct Hunt

Tech Stack

Tools used to build Resend

React EmailNode.jsTypeScriptNext.jsCustom email infrastructure

The full story

TL;DR

Zeno Rocha spent $25K on a domain, launched an open-source email library, built a 6,338-person waitlist in 7 weeks, then turned it into $5M ARR — the "Stripe of email."

Zeno Rocha had been frustrated by email at every company he'd worked at. As VP of Developer Experience at WorkOS and CPO at Liferay Cloud, he watched teams struggle with the same email problems: ugly HTML templates, unreliable delivery, terrible debugging. Email infrastructure felt stuck in 2005.

The Jab Before the Right Hook

In December 2022, before announcing Resend, Zeno launched React Email — an open-source library for building emails with React components. It was free, genuinely useful, and gave developers a taste of what modern email tooling could look like. This was the "jab" before the "right hook."

On January 4, 2023, Zeno publicly announced he was leaving WorkOS to build Resend. His announcement tweet — from an account with 39K followers — got 999K views and 4,634 likes. He positioned Resend as the "Stripe of email": clean API, great DX, just works.

The Waitlist

Instead of launching immediately, Zeno built a waitlist using Typeform. In 7 weeks: 6,338 signups. He documented every lesson publicly on his blog, including spending $25,000 on the resend.com domain for credibility.

YC and Launch

Resend entered Y Combinator's Winter 2023 batch. They launched publicly in June 2023, raised a $3M seed from SV Angel (with angels including Figma's Dylan Field, Vercel's Guillermo Rauch, and Supabase's Paul Copplestone), and crossed 100,000 users by April 2024. By June 2024: $5M ARR with just 22 people.

Domain cost: $25,000 (resend.com)
Announcement tweet: 999K views
Waitlist: 6,338 signups in 7 weeks
YC batch: W23
Users: 100,000 (April 2024)
$5M ARR with 22 people ($227K revenue per employee)

Key Takeaways

Open source as go-to-market — launch a free valuable tool first, then build the paid product on top

Personal brand matters enormously — 39K Twitter followers became the initial distribution channel

The "Stripe of X" positioning gives instant clarity on what you're building

Building in public creates anticipation and trust — document the journey openly

Domain credibility matters — $25K on resend.com signaled seriousness to developers

Originally published onZeno Rocha (Personal Blog)

Founder proof brief

A one-page proof brief turns Zeno's Resend playbook into your next test.

See what it covers before you sign up: the pattern worth copying, the channel to test, and the risk to avoid when you adapt this story.

Pattern

$10K MRR

Channel

Twitter / X

Output

Action checklist

What a proof brief covers

A one-page brief that turns Zeno's pattern into a testable plan
Channel bet: start from Twitter / X
A risk check before copying the Resend playbook

See what a proof brief covers

See what it covers first. Create an account only if you choose to unlock.

Inspired by Zeno's journey? Generate a business idea in the Developer tools space using AI and real founder data.

Milestone Journey

Zeno achieved 3 milestones on the path to $10K MRR

First customer

5 months

June 2023

Avg: 1 month

+3 months to next milestone

$1K MRR

8 months

September 2023

Avg: 6 months

+10 months to next milestone

$10K MRR

1 year

June 2024

Avg: 1 year

1 year

Total journey time

Milestones achieved

Against every documented journey

Zeno Rocha reached $10K MRR in 18 months, faster than 40% of the 295 documented $10K journeys (median 12 months). The amber bar is this journey.

See the full distribution

Zeno's Path to $10K MRRPremium

The journey, decisions, and context behind this milestone

How Zeno actually did it

7/7 funnel stages sourced

Reconstructed from Zeno's own published sources. Quoted claims are the founder's words, verified verbatim; anything marked as our analysis is exactly that.

Where the idea came from

Employer problemPivot from Not a direct pivot, but Resend was Zeno's second Y Combinator attempt. An earlier, unrelated consumer app ("LeCheese", a wine-and-cheese recommendation app built on Expo/Firebase) was rejected from YC's Winter 2020 batch in 2019. He applied again in 2022 with Resend, this time in a domain (DevTools/APIs/B2B) closer to his own experience, and was accepted into W23.

Zeno hit the same email problem twice as an employee before starting Resend: as CPO at Liferay Cloud he had high-profile customers complaining about deliverability, and later as VP of Developer Experience at WorkOS he again dealt with emails landing in spam. He and co-founder Bu first shipped React Email (an open-source templating library) as an exploration, then decided the deeper opportunity was the email-sending infrastructure itself, positioning Resend as a developer-first alternative to incumbents founded around 2009-2010.

“I faced the problem of sending emails at scale”

I'm starting my own company (zenorocha.com)

Validation

Built first, validated after

MvpValidated

Built an early prototype under throwaway placeholder domains (zeebbu.com, then klotty.com) before the product had the Resend name, brand, or domain, and put it directly in front of early adopters.

The klotty.com-branded prototype was shared with early adopters to get real usage before any public launch or naming decision.

“it was good enough to start putting it in the hands of early adopters”

Why I spent $25,000 on a domain (zenorocha.com)

WaitlistValidated6338 signups

Ran a public waitlist for about 7 weeks off the back of the founder's existing audience, using a landing page for signups and Typeform afterward to qualify and prioritize who to onboard first.

The waitlist grew to 6,338 signups in 7 weeks (a nearby YC launch-page snapshot two days later showed 6,469), driven mainly by the founder's own social following.

“growing a 6,338 people waitlist in 7 weeks”

Lessons learned from growing a 6,338 people waitlist in 7 weeks (zenorocha.com)

First test users

Existing audience~6338 usersFree testersTwitterLinkedIn

Zeno announced Resend directly to his existing Twitter following (39.4k people, built since 2009) and cross-posted the same announcement to LinkedIn; both drove waitlist sign-ups immediately.

“On January 4th, 2023 at 7:11 am PT, I published the first tweet about Resend”

Lessons learned from growing a 6,338 people waitlist in 7 weeks (zenorocha.com)

First paying customer

Personal networkFree to paid upgrade$10

In September 2022, once the MVP was working, Zeno and Bu gave it to a friend at another startup who started using it in production for free. To test whether the product was worth paying for, they sent him a $10 payment link, and he paid: the confidence from that single sale is what pushed them to apply to Y Combinator.

“We sent him a $10 payment link as a way to validate if the product was really good or not.”

What's next after 100,000 users (resend.com blog, byline Zeno Rocha)

Acquisition channels, and whether they worked

Twitter / XLaunchWorked

The launch-day tweet on January 4, 2023 at 7:11am PT was the primary trigger for waitlist growth.

“This tweet had 999.3k views, 4,634 likes, 352 retweets, and 282 replies.”

Lessons learned from growing a 6,338 people waitlist in 7 weeks (zenorocha.com)

Plausibly worked because Zeno had been posting on that Twitter account since 2009, building the 39.4k-follower audience over more than a decade before ever using it to launch a company.

Our analysis, not the founder's claim

Other · LinkedInLaunchWorked

Zeno is not a frequent LinkedIn poster but cross-posted the same Resend announcement there and it performed well.

“it got 107,411 views, 1,378 likes, and 156 comments”

Lessons learned from growing a 6,338 people waitlist in 7 weeks (zenorocha.com)

Other · Build in public (email updates to waitlist)Pre-launchWorked

After the initial announcement, the team kept the waitlist engaged with regular email updates about company news and product progress.

“we started sending them emails about company news and product updates”

Lessons learned from growing a 6,338 people waitlist in 7 weeks (zenorocha.com)

Communities · Y Combinator batch networkLaunchWorked

Resend offered YC-batch companies a direct skip-the-waitlist link, turning the accelerator's own network into an acquisition channel.

“YC companies - you can skip the 6,469 people waitlist using the secret link”

Launch YC: Resend - Email API for developers (Y Combinator launch post, written by Bu Kinoshita and Zeno Rocha)

What didn't work

OpsLaunchCost: time

The team hadn't load- or performance-tested the waitlist landing page on real mobile devices before the high-traffic launch.

“On the day we launched, we got several complaints about performance issues”

Lessons learned from growing a 6,338 people waitlist in 7 weeks (zenorocha.com)

They anticipated mobile sign-ups but did not budget time to test performance on real phones ahead of launch.

“we didn't spend too much time testing the performance on real phones”

Lessons learned from growing a 6,338 people waitlist in 7 weeks (zenorocha.com)

What they did instead: Fixed the performance issues during the launch window itself, but wished it had been done pre-launch.

OpsPre-launchCost: time

The low-friction, single-field waitlist signup form had no email confirmation step, so some sign-ups used fake addresses.

“people could still add fake email addresses”

Lessons learned from growing a 6,338 people waitlist in 7 weeks (zenorocha.com)

The team optimized the form for low friction (a single input field, no confirmation step) and only had light back-end validation.

“we had some back-end validation, people could still add fake email addresses”

Lessons learned from growing a 6,338 people waitlist in 7 weeks (zenorocha.com)

What they did instead: Integrated an email validation service (Emailable) to confirm addresses were real.

OpsPre-launchCost: time

There was no real plan for processing the waitlist once thousands of people had signed up, including a mandatory 1:1 onboarding call for every prospect.

“we didn't have a proper plan to process the waitlist”

Lessons learned from growing a 6,338 people waitlist in 7 weeks (zenorocha.com)

Requiring a manual onboarding call for every single waitlisted prospect could not scale with a 2-person team.

“We initially required every prospect to go through a mandatory onboarding call first (Superhuman style), but we quickly realized that wouldn't scale”

Lessons learned from growing a 6,338 people waitlist in 7 weeks (zenorocha.com)

What they did instead: Switched to automatically onboarding certain user segments and used a quick Typeform to qualify and prioritize the rest of the backlog.

How it changed as they grew

At launch: 2 people (Two co-founders, Zeno Rocha and Bu Kinoshita, who quit their jobs together and moved to San Francisco after Y Combinator accepted them.)

Accelerator · 2022-11

Seed · $3,000,000 · 2023-07

Series a plus · $18,000,000 · 2024-12

Sources (11 in the founder's own words)

I'm starting my own company (zenorocha.com) · founder-authored · 2023-01
Lessons learned from growing a 6,338 people waitlist in 7 weeks (zenorocha.com) · founder-authored · 2023-02
Resend raises $18M Series A (zenorocha.com) · founder-authored · 2024-12
YC Deal / Our YC story (resend.com, byline Zeno Rocha, Founder & CEO) · founder-authored
Resend (YC W23) raises $18M Series A (Hacker News, founder comments by zenorocha) · founder-authored · 2024-12
Launch YC: Resend - Email API for developers (Y Combinator launch post, written by Bu Kinoshita and Zeno Rocha) · founder-authored · 2023-02
Resend is built by indie hackers (Zeno Rocha, LinkedIn post) · founder-authored · 2024-09
Most people don't know this, but I got rejected from Y Combinator... (Zeno Rocha, LinkedIn post) · founder-authored · 2025-07
Resend raises $3M (resend.com blog, byline Zeno Rocha) · founder-authored · 2023-07
Why I spent $25,000 on a domain (zenorocha.com) · founder-authored · 2023-02
What's next after 100,000 users (resend.com blog, byline Zeno Rocha) · founder-authored · 2024-04

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Frequently asked questions

How much does Resend make?

Resend reports $25M ARR as of December 2025. Resend ~$25M revenue 2025 (400% YoY from $5M in 2024). $18M Series A from a16z Dec 2024. Source: Zeno Rocha (founder).

What is Resend?

Email API for developers that makes sending transactional and marketing emails as simple as Stripe made payments, with React-based email templating. It operates in Developer tools.

How long did it take Resend to reach $10k mrr?

Zeno Rocha took 1 year to reach $10k mrr with Resend.

Was Zeno Rocha a solo founder?

No. Zeno Rocha built Resend with co-founders.

What marketing channel did Resend use to grow?

Resend grew primarily through Twitter / X.

What industry is Resend in?

Resend operates in Developer tools.

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The full story

TL;DR

Zeno Rocha spent $25K on a domain, launched an open-source email library, built a 6,338-person waitlist in 7 weeks, then turned it into $5M ARR — the "Stripe of email."