# Email SDK (/docs/v/0.6.1)



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](/docs/v/0.6.1/adapters). Switching providers — or surviving an outage with a fallback route — never touches your application code.

```ts
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 [#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](/docs/v/0.6.1/adapters/field-support).
* **Retries and fallback routes, made explicit.** Exponential backoff inside an adapter, then explicit fallback adapters after it finally fails. [How routing works](/docs/v/0.6.1/concepts/fallbacks-and-retries).
* **Observable without leaking PII.** [Hooks](/docs/v/0.6.1/concepts/hooks) and the [observability plugin](/docs/v/0.6.1/plugins/built-in/observability) emit redacted events — counts and tag names, never bodies or recipients.
* **Testable for free.** [Memory and failing adapters](/docs/v/0.6.1/guides/test-email-behavior) plus the [capture plugin](/docs/v/0.6.1/plugins/built-in/capture) 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](/docs/v/0.6.1/reference/cli).

## Start here [#start-here]

<Cards>
  <Card title="Quickstart" href="/docs/v/0.6.1/getting-started/quickstart" description="Install, create a client, send your first email, and add a fallback in ~5 minutes." />

  <Card title="Choose an adapter" href="/docs/v/0.6.1/adapters" description="Browse all 20 providers and pick primary and backup routes." />

  <Card title="Production send pipeline" href="/docs/v/0.6.1/guides/production-send-pipeline" description="Retries, fallbacks, idempotency, observability, and tests for a real app." />

  <Card title="API reference" href="/docs/v/0.6.1/reference/client" description="Client options, the message shape, errors, and the CLI." />
</Cards>

## Beyond the core [#beyond-the-core]

<Cards>
  <Card title="Plugins" href="/docs/v/0.6.1/plugins" description="Shared defaults, observability, test capture, and typed client extensions." />

  <Card title="Convex Email Ops" href="/docs/v/0.6.1/components/convex-email" description="Queued sends from Convex with status tracking, retries, webhooks, and test mode." />

  <Card title="Build an adapter" href="/docs/v/0.6.1/guides/authoring/create-adapter" description="Wrap any provider API in the adapter contract and publish it for others." />

  <Card title="Agent skill" href="/docs/v/0.6.1/agents/skill" description="Teach Claude and other coding agents to integrate Email SDK correctly." />
</Cards>

## What it is not [#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.

<Callout title="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.
</Callout>