Send emails with AWS Lambda

AWS Lambda can send with either the TypeScript SDK or the REST API. Use environment variables or a secrets manager for the OpenSend API key.

Raw markdown

Environment variables

bash

OPENSEND_API_KEY=os_your_api_key
OPENSEND_BASE_URL=https://opensend.namuh.co

Set OPENSEND_BASE_URL to your self-hosted app URL if you are not using OpenSend Cloud.

TypeScript handler

import { Opensend } from "opensend";

const opensend = new Opensend(process.env.OPENSEND_API_KEY, {
  baseUrl: process.env.OPENSEND_BASE_URL,
});

type Event = {
  email?: string;
};

export async function handler(event: Event) {
  if (!event.email) {
    return { statusCode: 400, body: JSON.stringify({ error: "email is required" }) };
  }

  const { data, error } = await opensend.emails.send(
    {
      from: "OpenSend <onboarding@updates.example.com>",
      to: event.email,
      subject: "Hello from Lambda",
      html: "<p>AWS Lambda queued this email.</p>",
    },
    { idempotencyKey: `lambda-${event.email}` },
  );

  if (error) {
    return {
      statusCode: error.statusCode,
      body: JSON.stringify({ error: error.message, code: error.code }),
    };
  }

  return { statusCode: 200, body: JSON.stringify({ id: data.id }) };
}

Operational notes

Initialize the SDK outside the handler so warm invocations reuse it.
Use idempotency keys when Lambda is triggered by queues, EventBridge, or provider webhooks.
If your Lambda runs in a VPC, make sure it has outbound HTTPS access to OpenSend.
Prefer broadcasts for bulk audience sends; Lambda loops can accidentally exceed provider quotas.