Email Gateway (Multi-Provider)

Status: Production Ready ✅ Last Updated: 2026-01-10 Providers: Resend, SendGrid, Mailgun, SMTP2Go

Quick Start

Choose your provider based on needs:

Resend (Recommended for New Projects)

const response = await fetch('https://api.resend.com/emails', {
  method: 'POST',
  headers: {
    'Authorization': `Bearer ${env.RESEND_API_KEY}`,
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    from: '[email protected]',
    to: '[email protected]',
    subject: 'Welcome!',
    html: '<h1>Hello World</h1>',
  }),
});

const data = await response.json();
// { id: "49a3999c-0ce1-4ea6-ab68-afcd6dc2e794" }

SendGrid (Enterprise)

const response = await fetch('https://api.sendgrid.com/v3/mail/send', {
  method: 'POST',
  headers: {
    'Authorization': `Bearer ${env.SENDGRID_API_KEY}`,
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    personalizations: [{
      to: [{ email: '[email protected]' }],
    }],
    from: { email: '[email protected]' },
    subject: 'Welcome!',
    content: [{
      type: 'text/html',
      value: '<h1>Hello World</h1>',
    }],
  }),
});

// Returns 202 on success (no body)

Mailgun

const formData = new FormData();
formData.append('from', '[email protected]');
formData.append('to', '[email protected]');
formData.append('subject', 'Welcome!');
formData.append('html', '<h1>Hello World</h1>');

const response = await fetch(
  `https://api.mailgun.net/v3/${env.MAILGUN_DOMAIN}/messages`,
  {
    method: 'POST',
    headers: {
      'Authorization': `Basic ${btoa(`api:${env.MAILGUN_API_KEY}`)}`,
    },
    body: formData,
  }
);

const data = await response.json();
// { id: "<[email protected]>", message: "Queued. Thank you." }

SMTP2Go

const response = await fetch('https://api.smtp2go.com/v3/email/send', {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    api_key: env.SMTP2GO_API_KEY,
    to: ['<[email protected]>'],
    sender: '[email protected]',
    subject: 'Welcome!',
    html_body: '<h1>Hello World</h1>',
  }),
});

const data = await response.json();
// { data: { succeeded: 1, failed: 0, email_id: "..." } }

Provider Comparison

Features

Rate Limits (Free Tier)

API Limits

Message Limits

Configuration

Environment Variables

# Resend
RESEND_API_KEY=re_xxxxxxxxx

# SendGrid
SENDGRID_API_KEY=SG.xxxxxxxxx

# Mailgun
MAILGUN_API_KEY=xxxxxxxx-xxxxxxxx-xxxxxxxx
MAILGUN_DOMAIN=mg.yourdomain.com
MAILGUN_REGION=us  # or eu

# SMTP2Go
SMTP2GO_API_KEY=api-xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Wrangler Secrets (Cloudflare Workers)

# Set secrets
echo "re_xxxxxxxxx" | npx wrangler secret put RESEND_API_KEY
echo "SG.xxxxxxxxx" | npx wrangler secret put SENDGRID_API_KEY
echo "xxxxxxxx-xxxxxxxx-xxxxxxxx" | npx wrangler secret put MAILGUN_API_KEY
echo "api-xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx" | npx wrangler secret put SMTP2GO_API_KEY

# Deploy to activate
npx wrangler deploy

TypeScript Types

// Resend
interface ResendEmail {
  from: string;
  to: string | string[];
  subject: string;
  html?: