Zeno Rocha and Bu Kinoshita: The Founders Behind Resend’s Developer-Focused Email Platform

Email is easy to take for granted when it works. A password reset arrives, an order confirmation lands in the inbox, and a product update reaches its audience. To send these messages, software teams must create templates, connect an email service, set up the domains used to send emails, and track what happens after each email is sent.

Zeno Rocha and Bu Kinoshita started Resend to make that work feel more natural to developers. Their idea was to treat email as modern software infrastructure: something teams can build with familiar tools, test, and monitor. The company started with an open-source tool for creating email templates. It later built a platform for sending and managing emails.

The frustration behind the first lines of code

Before starting Resend, Rocha worked at two software companies where sending and managing emails was difficult. While working as chief product officer at Liferay Cloud and later as vice president of developer experience at WorkOS, he saw teams struggle with messages landing in spam and with the effort required to send email reliably at scale. In Resend’s launch post, he described those experiences as the reason he became interested in improving email infrastructure.

Rocha and Kinoshita also felt the friction of building email templates. Email has its own technical constraints: a template needs to display across a wide range of email clients, many of which handle formatting differently. In August 2022, the two began exploring a side project they described as the “Stripe of Email.” Their goal was to build an email platform around developers’ needs. Existing tools were mainly designed for marketing teams.

The first piece of that idea was React Email, an open-source project for building email templates with React. React is widely used in web development, so the approach offered developers a way to compose email layouts with components and familiar programming patterns. Resend’s company history says the project began in December 2022, after the founders became frustrated by how difficult it was to create modern templates that worked across email clients.

That starting point shaped Resend’s product philosophy: improve the developer experience around an essential but often overlooked part of software. Teams still need to send emails, but the code and infrastructure behind them do not have to feel disconnected from the rest of an application.

A $10 test became a company

The founders’ early validation was simple. After building a working version of Resend, they shared it with a friend at another startup. The friend began using it in production. Rocha and Kinoshita sent him a link to pay $10. They wanted to find out if he was willing to pay for the product. He did, which gave them confidence to apply to Y Combinator.

Resend joined Y Combinator’s Winter 2023 batch. The founding team included Rocha, Kinoshita, and Jonni Lundy, who joined in January 2023 as operations manager. Rocha is the company’s CEO, while Kinoshita is its CTO. The company’s materials describe Rocha’s background in product and developer experience, and Kinoshita’s experience building software products and developer tools.

The team moved quickly from a template project to a broader service. Resend was incorporated in January 2023, began shipping product improvements during launch weeks, and opened the platform to everyone in June 2023 after operating behind a waitlist. By early 2024, it had expanded beyond transactional messages to include marketing email capabilities.

Email made for the way developers build

Resend’s core product is an email API: a service that lets an application send messages through code rather than requiring a team to build and maintain its own sending infrastructure. Developers can use Resend’s APIs and software development kits to send transactional email, such as account confirmations and receipts. They can also use React Email to create the message templates themselves.

The appeal is partly about how the pieces fit together. A developer can build an email template and reuse it for future messages. They can send emails through the API and then check their delivery status. Resend’s platform also offers features such as domain verification, webhooks, and deliverability insights. Webhooks can notify an application about events such as bounces or unsubscribes, while delivery tools help teams investigate sending issues.

These tools are useful because email delivery is not fully controlled by the sending service. Sender reputation, domain setup, message quality, recipient engagement, and inbox-provider policies all affect whether a message reaches the inbox. Resend itself describes deliverability as a shared responsibility between the provider and the customer. No platform can guarantee that every email will reach the inbox. Teams still need to set up their email domains correctly and follow recommended practices when sending messages.

For developers, better observability matters as much as a simple send call. If a user never receives a login code or a payment notification, the team needs a way to inspect the message’s status and troubleshoot the cause. Resend’s early product pitch emphasized exposing email events rather than leaving teams uncertain about what happened after sending.

From transactional messages to broader communication

Transactional email remains central to Resend’s product, but the company has expanded into other parts of email communication. Its product lineup now includes tools for audiences, broadcasts, inbound email, automations, and templates. The expansion shows the company’s broader goal: to help developers manage more of the messages their software sends to users.

That does not mean every team should treat transactional and marketing email as the same task. Password resets and receipts are triggered by user actions and often need to arrive promptly. Newsletters and product announcements require audience management, consent practices, and thoughtful content planning. Resend’s growth into both areas gives teams a shared platform, while the work itself still calls for different rules and care.

The company’s trajectory has attracted significant interest. In December 2024, Resend announced an $18 million Series A led by Andreessen Horowitz. At that time, the company said more than 200,000 developers had signed up, and it reported that React Email had passed 300,000 weekly downloads on npm. These figures show Resend’s progress at the time of the funding announcement. They may have changed since then.

Why the developer experience matters

Email is not a new technology, but it remains a critical part of how people use online services. Developers need to send alerts, verification links, receipts, and updates in a way that fits the application they are building. When the tools for that work are difficult to integrate or troubleshoot, teams spend extra time on infrastructure instead of product improvements.

Rocha and Kinoshita’s approach is to make that work feel more familiar: use React for templates, APIs and SDKs to connect sending to applications, and product tools to help teams monitor delivery. The broader founding team has built Resend around the belief that small details—clear setup, useful documentation, and visible message events—can make email systems easier to work with.

Resend began as a response to a concrete developer frustration: designing emails that look right and ensuring they reach users. From React Email to a full sending platform, its evolution has followed that problem outward. Zeno Rocha and Bu Kinoshita helped turn an often-invisible piece of software infrastructure into a product developers can approach with the tools and patterns they already know.