Netlify Functions Quickstart

Prerequisites

To get the most out of this guide, you’ll need to:

Create a SendPost Account
Netlify Account (free tier works)
A Sub-Account API Key from your SendPost dashboard

You can find your API keys in your SendPost Dashboard. Make sure to use your Sub-Account API Key for sending emails.

1. Install Dependencies

npm

npm install sendpost-js-sdk

2. Project Structure

Create a Netlify function:

netlify/
  functions/
    send-email.js

Or if using TypeScript:

netlify/
  functions/
    send-email.ts

3. Basic Email Function

Create netlify/functions/send-email.js:

JavaScript

const sendpost = require('sendpost-js-sdk');

const emailApi = new sendpost.EmailApi();

exports.handler = async (event, context) => {
  // Handle CORS
  const headers = {
    'Access-Control-Allow-Origin': '*',
    'Access-Control-Allow-Headers': 'Content-Type',
    'Access-Control-Allow-Methods': 'POST, OPTIONS',
  };

  if (event.httpMethod === 'OPTIONS') {
    return {
      statusCode: 200,
      headers,
      body: '',
    };
  }

  if (event.httpMethod !== 'POST') {
    return {
      statusCode: 405,
      headers,
      body: JSON.stringify({ error: 'Method not allowed' }),
    };
  }

  try {
    const { to, subject, htmlBody, textBody } = JSON.parse(event.body);

    if (!to || !subject || !htmlBody) {
      return {
        statusCode: 400,
        headers,
        body: JSON.stringify({
          success: false,
          error: 'Missing required fields: to, subject, htmlBody',
        }),
      };
    }

    const emailMessage = new sendpost.EmailMessage();
    emailMessage.from = {
      email: 'hello@playwithsendpost.io',
      name: 'SendPost',
    };
    emailMessage.to = [{ email: to }];
    emailMessage.subject = subject;
    emailMessage.htmlBody = htmlBody;
    emailMessage.textBody = textBody || htmlBody.replace(/<[^>]*>/g, '');
    emailMessage.trackOpens = true;
    emailMessage.trackClicks = true;

    const response = await emailApi.sendEmail(
      process.env.SENDPOST_API_KEY,
      { emailMessage }
    );

    return {
      statusCode: 200,
      headers: {
        ...headers,
        'Content-Type': 'application/json',
      },
      body: JSON.stringify({
        success: true,
        messageId: response.messageId,
      }),
    };
  } catch (error) {
    console.error('SendPost error:', error);
    return {
      statusCode: 500,
      headers: {
        ...headers,
        'Content-Type': 'application/json',
      },
      body: JSON.stringify({
        success: false,
        error: error.message,
      }),
    };
  }
};

TypeScript Version

Create netlify/functions/send-email.ts:

TypeScript

import { Handler } from '@netlify/functions';
import sendpost from 'sendpost-js-sdk';

const emailApi = new sendpost.EmailApi();

export const handler: Handler = async (event, context) => {
  const headers = {
    'Access-Control-Allow-Origin': '*',
    'Access-Control-Allow-Headers': 'Content-Type',
    'Access-Control-Allow-Methods': 'POST, OPTIONS',
  };

  if (event.httpMethod === 'OPTIONS') {
    return {
      statusCode: 200,
      headers,
      body: '',
    };
  }

  if (event.httpMethod !== 'POST') {
    return {
      statusCode: 405,
      headers,
      body: JSON.stringify({ error: 'Method not allowed' }),
    };
  }

  try {
    const { to, subject, htmlBody, textBody } = JSON.parse(event.body);

    if (!to || !subject || !htmlBody) {
      return {
        statusCode: 400,
        headers,
        body: JSON.stringify({
          success: false,
          error: 'Missing required fields: to, subject, htmlBody',
        }),
      };
    }

    const emailMessage = new sendpost.EmailMessage();
    emailMessage.from = {
      email: 'hello@playwithsendpost.io',
      name: 'SendPost',
    };
    emailMessage.to = [{ email: to }];
    emailMessage.subject = subject;
    emailMessage.htmlBody = htmlBody;
    emailMessage.textBody = textBody || htmlBody.replace(/<[^>]*>/g, '');
    emailMessage.trackOpens = true;
    emailMessage.trackClicks = true;

    const response = await emailApi.sendEmail(
      process.env.SENDPOST_API_KEY!,
      { emailMessage }
    );

    return {
      statusCode: 200,
      headers: {
        ...headers,
        'Content-Type': 'application/json',
      },
      body: JSON.stringify({
        success: true,
        messageId: response.messageId,
      }),
    };
  } catch (error: any) {
    console.error('SendPost error:', error);
    return {
      statusCode: 500,
      headers: {
        ...headers,
        'Content-Type': 'application/json',
      },
      body: JSON.stringify({
        success: false,
        error: error.message,
      }),
    };
  }
};

4. Environment Variables

Create netlify.toml:

[build]
  functions = "netlify/functions"

[build.environment]
  SENDPOST_API_KEY = "your_sub_account_api_key"

Or set in Netlify Dashboard:

Go to Site settings → Environment variables
Add SENDPOST_API_KEY

5. Common Use Cases

Welcome Email Function

Create netlify/functions/welcome-email.js:

JavaScript

const sendpost = require('sendpost-js-sdk');

const emailApi = new sendpost.EmailApi();

exports.handler = async (event, context) => {
  const headers = {
    'Access-Control-Allow-Origin': '*',
    'Access-Control-Allow-Headers': 'Content-Type',
    'Access-Control-Allow-Methods': 'POST, OPTIONS',
  };

  if (event.httpMethod === 'OPTIONS') {
    return { statusCode: 200, headers, body: '' };
  }

  try {
    const { email, firstName } = JSON.parse(event.body);

    const emailMessage = new sendpost.EmailMessage();
    emailMessage.from = {
      email: 'hello@playwithsendpost.io',
      name: 'SendPost',
    };
    emailMessage.to = [{
      email,
      name: firstName,
      customFields: { firstName },
    }];
    emailMessage.subject = 'Welcome {{firstName}}!';
    emailMessage.htmlBody = `
      <h1>Welcome, {{firstName}}!</h1>
      <p>Thank you for joining us. We're excited to have you on board.</p>
      <p><a href="{{unsubscribe}}">Unsubscribe</a></p>
    `;
    emailMessage.groups = ['welcome'];

    const response = await emailApi.sendEmail(
      process.env.SENDPOST_API_KEY,
      { emailMessage }
    );

    return {
      statusCode: 200,
      headers: { ...headers, 'Content-Type': 'application/json' },
      body: JSON.stringify({
        success: true,
        messageId: response.messageId,
      }),
    };
  } catch (error) {
    return {
      statusCode: 500,
      headers: { ...headers, 'Content-Type': 'application/json' },
      body: JSON.stringify({ success: false, error: error.message }),
    };
  }
};

6. Testing Locally

Install Netlify CLI:

npm install -g netlify-cli

Run locally:

netlify dev

Test your function:

curl -X POST http://localhost:8888/.netlify/functions/send-email \
  -H "Content-Type: application/json" \
  -d '{
    "to": "user@example.com",
    "subject": "Test Email",
    "htmlBody": "<h1>Hello from Netlify!</h1>"
  }'

7. Deploy

Deploy to Netlify:

netlify deploy --prod

Or connect your Git repository for automatic deployments.

Make sure your sender email domain is verified in your SendPost account before sending emails.

8. Next Steps

Explore more examples and use cases: