Email Gateway (Multi-Provider)

Multi-provider email sending skill for Cloudflare Workers and Node.js applications. Comprehensive coverage of Resend, SendGrid, Mailgun, and SMTP2Go APIs.

Auto-Trigger Keywords

This skill should be suggested when the user mentions:

Technology Names:

• resend, resend api, resend.com
• sendgrid, sendgrid api, twilio sendgrid
• mailgun, mailgun api
• smtp2go, smtp2go api
• email api, email service, email provider
• transactional email, transactional emails

Use Cases:

• send email, sending emails, email delivery
• password reset email, verification email, confirmation email
• bulk email, batch email, mass email
• email templates, dynamic templates, react email
• email webhooks, bounce handling, complaint handling
• email attachments, file attachments
• smtp relay, email relay

Error Messages:

• "unauthorized" (resend, sendgrid, mailgun, smtp2go)
• "validation error" (resend, smtp2go)
• "rate limit exceeded" (resend, sendgrid, mailgun, smtp2go)
• "domain not verified" (resend, sendgrid, mailgun, smtp2go)
• "invalid email format" (all providers)
• "payload too large" (sendgrid)
• "attachment size exceeds" (resend, sendgrid, mailgun)
• "invalid template id" (sendgrid, mailgun)
• "failed to deliver" (all providers)

React Email:

• react email, react-email, @react-email/components
• jsx email, component email, email components
• html email templates, responsive email

Webhooks:

• email bounced, email delivered, email opened, email clicked
• bounce webhook, delivery webhook, open tracking, click tracking
• spam complaint, unsubscribe webhook
• webhook signature, verify webhook, webhook verification

Migration:

• switch from sendgrid to resend
• migrate from mailgun to sendgrid
• change email provider, email provider abstraction

What This Skill Covers

1. Provider Setup - Configuration for Resend, SendGrid, Mailgun, SMTP2Go
2. Sending Patterns - Transactional, batch, templates, attachments
3. React Email - Component-driven email design (Resend)
4. Dynamic Templates - Handlebars/variable substitution
5. Webhooks - Event tracking, signature verification, bounce handling
6. Error Handling - Provider-specific error codes and recovery
7. Rate Limiting - Exponential backoff, quota tracking
8. Migration - Provider abstraction layer for switching
9. Testing - Connectivity tests, test mode sending

Quick Example

// Resend - Modern, React Email support
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: 'noreply@yourdomain.com',
    to: 'user@example.com',
    subject: 'Welcome!',
    html: '<h1>Hello World</h1>',
  }),
});

// SendGrid - Enterprise scale
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: 'user@example.com' }],
    }],
    from: { email: 'noreply@yourdomain.com' },
    subject: 'Welcome!',
    content: [{
      type: 'text/html',
      value: '<h1>Hello World</h1>',
    }],
  }),
});

Related Skills

• cloudflare-worker-base - Cloudflare Workers setup
• react-hook-form-zod - Form validation before sending
• project-planning - Planning email features in applications