Developer API

Send and receive email with one HTTP call

A small, versioned HTTP API for sending, listing, reading, replying, forwarding, and transferring attachments — hosted on your deployment.

View pricing Talk to our team

Plain HTTP, no SDK

Any language that can make an HTTP request can send email.

Send & receive

The same simple API covers outbound and reading your inbox.

Simple auth

Personal `sk-` API keys with simple Bearer authentication.

Runs on your domain

No third-party endpoint — the API lives on your Cloudflare.

example.ts

// One HTTP call — runs on your own domain & Cloudflare.
await fetch("https://mail.yourdomain.com/openapi/v1/emails/send", {
  method: "POST",
  headers: {
    Authorization: `Bearer ${MARKRELAY_API_KEY}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    from: "Acme <no-reply@yourdomain.com>",
    to: "user@example.com",
    subject: "Welcome aboard 🎉",
    html: "<p>Thanks for signing up!</p>",
  }),
});

Explore more of MarkRelay

Multi-Domain Mailboxes

Own your email stack today

Buy MarkRelay once and run it in your Cloudflare account. MarkRelay adds no per-message or per-seat charge; Cloudflare usage and service limits remain separate.

View pricing