Quickstart

Install the SDK:

bun add @opencoredev/email-sdk

This example sends through Resend. Set RESEND_API_KEY in the environment before running it.

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 to Acme",
  text: "Your account is ready.",
});

Add built-in SMTP fallback

Add SMTP when you want a second route for the same transactional email. The SMTP adapter is built in and does not require Nodemailer. When SMTP auth is configured on a non-secure connection, Email SDK upgrades with STARTTLS before authenticating.

Only use fallback adapters that can send the same message shape. For example, SMTP supports address fields and headers, but not provider-only fields like tags, metadata, or attachments.

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

export const email = createEmailClient({
  adapters: [
    resend({ apiKey: process.env.RESEND_API_KEY! }),
    smtp({
      host: "smtp.purelymail.com",
      port: 587,
      auth: {
        user: process.env.SMTP_USER!,
        pass: process.env.SMTP_PASS!,
      },
    }),
  ],
  fallback: ["smtp"],
});

Your application still sends the same way:

await email.send({
  from: "Acme <hello@acme.com>",
  to: "user@example.com",
  subject: "Receipt",
  text: "Thanks for your order.",
});

Check the result

send resolves with the normalized adapter response. The provider value tells you which adapter actually handled the send.

const result = await email.send(message);

console.log(result.provider);
console.log(result.id);

If the adapter returns a message ID, Email SDK exposes it as both id and messageId. Provider responses are still available through raw when an adapter includes them.

Test from the CLI

Use the CLI to check adapter credentials from your terminal.

email-sdk doctor --adapter resend

Send a test email:

email-sdk send \
  --adapter resend \
  --from "Acme <hello@acme.com>" \
  --to "user@example.com" \
  --subject "Hello" \
  --text "It works"

Use --dry-run when you want to validate the message and selected adapter without sending email.

Add built-in SMTP fallback

Check the result

Test from the CLI

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