Key Takeaways

  • Zeno Rocha modeled Resend's growth on Vercel's relationship with Next.js, building React Email as an open-source top-of-funnel acquisition channel.
  • User research for Resend revealed that developers hated hand-coding nested HTML tables and inline styles for legacy clients like Outlook far more than they cared about SMTP APIs.
  • Rocha personally wrote integration documentation showing engineers how to use React Email with direct competitors like SendGrid, Mailchimp, and Mailgun.
  • React Email functions as a compiler: developers write standard JSX components, and the engine compiles that code into reliable HTML that renders across disparate email clients.

Build for Your Competitors' Customers First

When building Resend, Rocha interviewed dozens of software engineers. He expected to hear complaints about deliverability or API speed. Instead, he found that everyone hated building templates. Developers still had to hand-craft nested HTML tables and inline CSS hacks to support desktop Outlook. Rocha realized the real headache occurred when authoring the template, long before anyone called an SMTP API.

To solve that, he built React Email. The project let engineers write email templates in React, translating standard JSX components into clean HTML. As swyx observed during the conversation, React Email succeeds because it operates as an abstraction layer: “So like to me the reason that React works is that it is basically a compiler. It's like it's like well somebody writes this once and then as long as you fit the API it's going to work everywhere.” (play from 25:48)

Most founders who build a developer tool immediately lock it behind their own proprietary product. Rocha took the opposite path. He wanted developers who used SendGrid, Mailchimp, and Mailgun to adopt React Email immediately.

“If you go to the docs, for example, you'll find there are docs about how do you set this up with SendGrid and Mailchimp and Mailgun,” (play from 24:13) Rocha explained. “I wrote every single one of those docs over there.” (play from 24:21)

By writing thorough documentation for competing delivery services, Rocha removed any barrier to adoption. An engineer working on a legacy SendGrid codebase did not need permission from their manager to switch providers. They could adopt React Email on Monday morning, fix their rendering bugs, and leave their delivery infrastructure untouched.

The Next.js Playbook for Email

Resend did not treat React Email as a casual side project. It was the core of their developer acquisition strategy.

“React email is our nextjs, right? So we wanted like an open-source channel for top of the funnel,” (play from 24:01) Rocha stated.

Vercel proved this model by giving developers an open-source framework, then selling the hosting infrastructure to deploy it. Rocha saw the same opening in transactional email. If you win the developer when they write the template, you own the conversation when they pick an API to deliver it.

This approach created an advantage against entrenched competitors. Incumbents like SendGrid or Mailgun had spent years optimizing delivery backends, but their developer interfaces felt outdated. By capturing developers at the creation layer, Resend made incumbent APIs feel like invisible plumbing.

Rocha summarized the philosophy simply: “it was a strategy of like we're gonna give give and then we ask uh and if people are like building the like the email template using react like now they need a platform to send it where do they do that here's resend.” (play from 24:31)

The wedge works because developers do not want to stitch together separate tools. Once an engineer builds a template inside React Email, the path of least resistance is to send it through Resend's native pipeline. By giving away practical software upfront without demanding an account signup, Rocha turned an open-source library into an engine that pulled qualified developers directly into Resend's paid service.

What to Do With This

Map the workflow that happens immediately before a customer touches your core paid product. If you sell an API or a database, identify the painful boilerplate code your user must write before making their first request. Build a standalone, open-source tool that solves that specific pain point, and publish step-by-step setup guides for your three biggest competitors. Give developers the tool for free, earn their trust during development, and become the obvious default when they push to production.