Email SDK Documentation - TypeScript email SDK

One typed send() for 20 email providers — explicit routing, retries, fallbacks, and zero dependencies.

Email SDK is a zero-dependency TypeScript library for transactional email. You write one typed message; configured adapters decide how it reaches Resend, Postmark, SendGrid, AWS SES, Mailgun, SMTP, or any of 20 providers. Switching providers — or surviving an outage with a fallback route — never touches your application code.

import { createEmailClient } from "@opencoredev/email-sdk";
import { resend } from "@opencoredev/email-sdk/resend";

const email = createEmailClient({
  adapters: [resend({ apiKey: process.env.RESEND_API_KEY! })],
});

await email.send({
  from: "Acme <hello@acme.com>",
  to: "user@example.com",
  subject: "Welcome",
  text: "Your account is ready.",
});

Why Email SDK

One message shape, 20 providers. Import only the adapter you use — each one is a separate entry point, and the core has zero runtime dependencies.
No silent data loss. Providers differ: Resend has no metadata, SMTP has no tags. Adapters either map a field or throw before the request — never drop it. See field support.
Retries and fallback routes, made explicit. Exponential backoff inside an adapter, then explicit fallback adapters after it finally fails. How routing works.
Observable without leaking PII. Hooks and the observability plugin emit redacted events — counts and tag names, never bodies or recipients.
Testable for free. Memory and failing adapters plus the capture plugin assert send behavior without a real provider.
A CLI for the boring parts. email-sdk doctor checks your environment, --dry-run validates a message against an adapter, and send runs a real smoke test. CLI reference.

Start here

Quickstart

Install, create a client, send your first email, and add a fallback in ~5 minutes.

Choose an adapter

Browse all 20 providers and pick primary and backup routes.

Production send pipeline

Retries, fallbacks, idempotency, observability, and tests for a real app.

API reference

Client options, the message shape, errors, and the CLI.

Beyond the core

Plugins

Shared defaults, observability, test capture, and typed client extensions.

Convex Email Ops

Queued sends from Convex with status tracking, retries, webhooks, and test mode.

Build an adapter

Wrap any provider API in the adapter contract and publish it for others.

Agent skill

Teach Claude and other coding agents to integrate Email SDK correctly.

What it is not

Email SDK is not a campaign tool, queue, template engine, or hosted analytics product. It is the layer apps keep rebuilding — adapter setup, one consistent send call, typed errors, compatibility checks, and fallback routes explicit enough to debug at 3 a.m.

Local checks are not deliverability

The SDK validates message shape and field support before every request, but live delivery still depends on your provider account: verified sender domains, API scopes, regions, and sandbox rules. Dry-run first, then run one real smoke send from your production environment.

Email SDK