# Resend Resend is an email platform built for developers. You send email through a REST API, through SDKs for most popular languages, or through plain SMTP. The same account also handles marketing broadcasts, contacts, automations and inbound email, so one provider covers both the "your password reset link" emails and the newsletter. In the [[Email Service Provider (ESP)]] space, it sits next to Postmark and SendGrid for transactional email, and next to newsletter tools for broadcasts. The team's starting point is a question they put on their About page: "The web has come a long way in the last ten years, but why is email stuck in the past?" Writing HTML email still means nested tables and inline styles, and the hardest part of email (deliverability, i.e., landing in the inbox instead of the spam folder) is mostly invisible until it goes wrong. Resend tries to fix both. ## Origin Resend started in 2022 as an open source project, React Email, out of frustration with building modern email templates. React Email lets you write emails as [[React]] components that compile to email-safe HTML. The sending platform came next and launched in 2023, after the team went through [[Y Combinator]] (Winter 2023 batch). The founders are Zeno Rocha, Bu Kinoshita and Jonni Lundy, with Zeh Fernandes also part of the leadership. The company is fully remote and backed by Y Combinator, a16z and SV Angel, plus angel investors that include the founders of Figma, [[Vercel]], Sentry and [[Supabase]]. ## What it covers ### Transactional email The core use case: emails your application sends in response to something a user did (sign-up, sign-in codes, receipts, alerts). - Send one email per call, or up to 100 in a single batch call - Schedule emails with an ISO 8601 date or in natural language ("tomorrow at 9am ET"), and cancel them before they go out - Idempotency keys, so a retried request doesn't send the same email twice (see [[Idempotency]]) - Attachments, inline images, custom headers and unsubscribe headers - Test addresses such as `[email protected]` to simulate deliveries, bounces and complaints, and a sandbox sender (`[email protected]`) to try things before you verify a domain ### Templates and React Email Templates have an editor, variables and version history. React Email plugs in directly: you write the email as a React component and Resend renders it. There is also an embeddable React Email editor if you want to offer email editing inside your own product. ### Broadcasts Broadcasts are the marketing side: newsletters and announcements sent to a segment of your contacts. You get an editor, sending through the API, performance tracking, the list of clicked links, and you can cancel or duplicate a broadcast. ### Contacts, segments and topics Contacts carry custom properties. Segments group them, and topics let people choose what they want to receive (preference-based subscriptions instead of all-or-nothing). Resend also manages the unsubscribe list, a custom unsubscribe page, CSV import and audience hygiene. ### Automations Event-driven workflows built from steps: a trigger, conditions, delays, "wait for event", send email, add to segment, update or delete a contact. You can send custom events from your application to drive them, and monitor each run. ### Receiving email and inboxes Resend also receives email. You configure a custom receiving domain, get a webhook for each inbound message, and can fetch its content and attachments, forward it or reply to it. On top of that, Inboxes (with labels, threads, drafts and agent settings) are aimed at [[AI Agents]] that need their own mailbox to read and answer email. ### Domains and deliverability You send from your own domain once you've verified it with DNS records: - SPF lists the servers allowed to send for your domain - DKIM signs each email cryptographically, so receivers can check it wasn't forged or altered - DMARC tells receivers what to do when SPF or DKIM checks fail, and sends you reports - BIMI displays your brand logo next to your emails in supporting inboxes, once DMARC is enforced Beyond that: opportunistic or enforced TLS, a custom return path, sending regions, domain claiming, dedicated IPs with warm-up, open and click tracking, deliverability insights, and suppression and bounce management. Resend also publishes a free, open source DMARC analyzer. ### Webhooks Webhooks report email events (sent, delivered, bounced, complained, opened, clicked, failed, received, scheduled, suppressed) plus domain, contact and inbox events. Payloads are signed so you can verify them, failed deliveries are retried and can be replayed, and there's a self-hosted Webhook Ingester if you'd rather receive them on your own infrastructure. ### SMTP relay If a tool can't call an API but can speak SMTP, it can still send through Resend. The docs cover Nodemailer, PHPMailer, Django, [[Laravel]], Rails, WordPress, [[Supabase]], NextAuth and Customer.io. ### Logs, metrics and team features API request logs, a Metrics API, teams, SSO, multi-factor authentication, and the usual security and compliance documents (including a DPA). ### SDKs and frameworks Official SDKs exist for [[Node.js]], [[PHP]], [[Python]], Ruby, [[Go]], [[Rust]], Elixir, Java and .NET. The quickstarts cover most web frameworks ([[Next.js]], Remix, Nuxt, SvelteKit, Astro, Express, Hono, [[Bun]], Laravel, Symfony, Rails, Django, FastAPI, Flask, Axum, Phoenix...) and serverless runtimes (Vercel Functions, Cloudflare Workers, Supabase Edge Functions, Deno Deploy, AWS Lambda). Details in [[Resend API]]. ### Integrations [[n8n]], Auth0, Better Auth, Attio, Stripe Projects, the Vercel Marketplace and Appwrite. AI app builders (Lovable, v0, Bolt.new, Replit) can wire up Resend for you. The Vercel Chat SDK uses it for conversational email. For platforms that send on behalf of their own customers, the docs cover an OAuth client setup and multi-tenant configurations. ## Built for agents too Resend treats AI agents as first-class users of the platform, next to humans: - [[Resend MCP Server]]: a remote or local [[Model Context Protocol (MCP)]] server, so agents like [[Claude Code]] can send email and manage the account - [[Resend CLI]]: a [[Command Line Interface (CLI)|command-line tool]] that switches to JSON output when an agent pipes it, with proper exit codes, idempotency and scheduling - [[Resend Agent Skills]]: ready-made [[AI Agent Skills]] that teach agents how to send email, build React Email templates and handle inbound mail safely - [[Resend Headless Dashboard Initiative]]: the rule that everything the dashboard can do must also be possible through the API, CLI and MCP server - An `llms.txt` file for the docs and an AI onboarding guide Put together, an agent can set up a domain, create a segment, launch a broadcast and check its metrics without a human opening the dashboard. ## How I use it I use Resend to send the sign-in emails (magic links and codes) of the Knowii account system from the knowii.net domain, and from some of my [[n8n]] workflows. ## References - Website: https://resend.com - Documentation: https://resend.com/docs - About: https://resend.com/about - Docs for LLMs (llms.txt): https://resend.com/docs/llms.txt - Headless Dashboard Initiative (Resend blog, 2026-09-22): https://resend.com/blog/headless-dashboard-initiative ## Related - [[Resend API]] - [[Resend MCP Server]] - [[Resend CLI]] - [[Resend Agent Skills]] - [[Resend Headless Dashboard Initiative]] - [[Email Service Provider (ESP)]] - [[Cloudflare Email Routing and Sending]] - [[React]] - [[Y Combinator]] - [[n8n]] - [[Software as a Service (SaaS)]] - [[AI Agents]]