OpenSend keeps the familiar Resend API shape, swaps in os_ keys, and runs on your own infrastructure. Start with the send path, then expand into domains, audience, broadcasts, webhooks, OpenAPI, and MCP.
Quickstart
Base URL: https://api.opensend.com
import { Resend } from "opensend";
const resend = new Resend(process.env.OPENSEND_API_KEY);
const { data, error } = await resend.emails.send({
from: "OpenSend <onboarding@updates.example.com>",
to: ["user@example.com"],
subject: "Hello from OpenSend",
html: "<strong>It works.</strong>",
});
if (error) throw error;
console.log(data); // { id: "..." }For production, verify a sending domain first. Use a real recipient only after your domain records are healthy.
OpenSend guides
REST basics
Use os_ API keys with Bearer auth. Dashboard sessions are separate from API authentication.
Sending
Send HTML or text email, schedule delivery, attach metadata, and protect retries with idempotency keys.
SDK
Install the opensend package, initialize the client, and send email from your application code.
AI clients
Use llms.txt, OpenAPI, and the MCP server to give agents a stable OpenSend control surface.
157
markdown docs
OpenAPI 3.0
machine-readable contract
16
highlighted API examples
Docs corpus
Endpoints, auth, pagination, errors, quotas, and resource operations.
Sending, batch, scheduling, attachments, receiving, tags, and idempotency.
Contacts, segments, topics, properties, unsubscribes, and preferences.
Broadcasts, templates, variables, versioning, and performance tracking.
Event types, signed requests, retries, replays, and lifecycle payloads.
Self-hosting, ingester deploys, observability, security, and troubleshooting.
Emails
/emailsAccepts the Resend-compatible send body. Duplicate Idempotency-Key retries within 24 hours replay the original accepted id.
await resend.emails.send({
from: "Acme <onboarding@example.com>",
to: ["user@example.com"],
subject: "Welcome",
html: "<p>Hello world</p>",
});/emails/batchQueue multiple messages in one request. The batch idempotency key protects the whole accepted envelope.
await resend.emails.sendBatch([
{
from: "Acme <news@example.com>",
to: ["a@example.com"],
subject: "For A",
html: "<p>A</p>",
},
{
from: "Acme <news@example.com>",
to: ["b@example.com"],
subject: "For B",
html: "<p>B</p>",
},
]);/emails/:email_id/cancelCancel a scheduled message before it leaves the queue.
await resend.emails.cancel("email_id");/api/emails/:idOpenSend dashboard/API detail route for status, metadata, and lifecycle events.
const email = await client.emails.get("email_id");Domains
/api/domainsAdd a domain and receive the DNS records required for SES-backed sending.
await client.domains.create({ name: "updates.example.com" });/api/domains/:id/auto-configureOperator/self-host Cloudflare token flow for writing the generated records automatically.
await fetch("https://api.opensend.com/api/domains/domain_id/auto-configure", {
method: "POST",
headers: { Authorization: "Bearer " + apiKey },
});/api/domains/:idInspect verification status and copy DNS records.
const domain = await client.domains.get("domain_id");Audience
/contactsCreate a contact through the Resend-compatible root alias.
await client.contacts.create({
email: "jane@example.com",
firstName: "Jane",
});/segmentsCreate a named audience segment for filtering contacts and campaigns.
await client.segments.create({ name: "Active users" });/segments/:id/contactsFetch contacts that currently match a segment.
const contacts = await client.segments.listContacts("segment_id");Campaigns
/broadcastsCreate a draft broadcast with sender, subject, segment, and preview text.
await client.broadcasts.create({
name: "March newsletter",
from: "Acme <news@example.com>",
subject: "March updates",
segmentId: "segment_id",
});/broadcasts/:id/sendSend immediately or schedule with the same narrow natural-language window as email sends.
await client.broadcasts.send("broadcast_id", {
scheduledAt: "in 1 hour",
});/templatesStore versioned HTML templates that can be rendered for future sends.
await client.templates.create({
name: "Welcome",
alias: "welcome",
subject: "Welcome",
html: "<p>Hi {{name}}</p>",
});Platform
/api-keysCreate scoped keys. OpenSend keys use the os_ prefix while preserving Resend-compatible API semantics.
await client.apiKeys.create({ name: "Production" });/api/webhooksSubscribe an HTTPS endpoint to signed delivery and lifecycle events.
await fetch("https://api.opensend.com/api/webhooks", {
method: "POST",
headers: {
Authorization: "Bearer " + apiKey,
"Content-Type": "application/json",
},
body: JSON.stringify({
endpoint: "https://example.com/webhooks/opensend",
events: ["email.delivered"],
}),
});/openapi.jsonUnauthenticated OpenAPI 3.0 contract for SDKs, generated clients, and audits.
const spec = await fetch("https://api.opensend.com/openapi.json").then((res) => res.json());LLM docs
OpenSend exposes the canonical LLM entrypoint at /docs/llms.txt so coding agents can discover the API, SDKs, MCP server, operational setup, and parity notes before generating integration code.
{
"mcpServers": {
"opensend": {
"command": "bun",
"args": ["/path/to/opensend/packages/mcp/src/stdio.ts"],
"env": {
"OPENSEND_API_KEY": "os_YOUR_API_KEY",
"OPENSEND_API_BASE_URL": "https://api.opensend.com"
}
}
}
}