Resend

Overview

Resend is the recommended email provider for ShipFree in production. It’s a modern email API built for developers with:

Simple, intuitive API
Built-in React Email support
Excellent deliverability rates
Generous free tier (3,000 emails/month)
Native batch email support
Comprehensive analytics and logging

Resend is the first provider ShipFree checks for during auto-discovery. If you have RESEND_API_KEY set, it will be used automatically.

Prerequisites

A Resend account
A verified domain (or use Resend’s test domain for development)

Setup Instructions

Step 1: Get Your API Key

Sign up or log in at resend.com
Navigate to API Keys in the dashboard
Click Create API Key
Give it a name (e.g., “ShipFree Production”)
Copy the API key (it starts with re_)

Save your API key immediately - Resend only shows it once for security.

Step 2: Verify Your Domain (Production)

For production use, you need to verify a domain:

Go to Domains in the Resend dashboard
Click Add Domain
Enter your domain (e.g., yourdomain.com)
Add the provided DNS records to your domain registrar:
- SPF record
- DKIM record
- DMARC record (optional but recommended)
Wait for DNS propagation (usually 5-15 minutes)
Click Verify in Resend dashboard

Use a subdomain like mail.yourdomain.com to keep email DNS records separate from your main domain.

Step 3: Configure Environment Variables

Add these variables to your .env file:

# Required
RESEND_API_KEY=re_your_api_key_here

# Optional - specify sending domain (defaults to verified domain)
RESEND_DOMAIN=mail.yourdomain.com

# Optional - explicitly set Resend as provider
EMAIL_PROVIDER=resend

# Email defaults
DEFAULT_FROM_EMAIL=noreply@yourdomain.com
DEFAULT_FROM_NAME=Your App Name

Step 4: Test Your Configuration

Send a test email:

import { sendEmail, getActiveProviderName } from '@/lib/messaging/email';

// Verify Resend is active
console.log('Active provider:', getActiveProviderName()); // Should output: 'resend'

// Send test email
const result = await sendEmail({
  to: 'your-email@example.com',
  subject: 'Test from ShipFree',
  html: '<h1>Success!</h1><p>Resend is working correctly.</p>',
});

if (result.success) {
  console.log('Email sent successfully!', result.data);
} else {
  console.error('Email failed:', result.message);
}

Features

Batch Email Support

Resend has native batch sending support, which ShipFree automatically uses:

import { sendBatchEmails } from '@/lib/messaging/email';

await sendBatchEmails({
  emails: [
    {
      to: 'user1@example.com',
      subject: 'Welcome!',
      html: '<p>Welcome user 1</p>',
    },
    {
      to: 'user2@example.com',
      subject: 'Welcome!',
      html: '<p>Welcome user 2</p>',
    },
  ],
});

Resend’s batch API can send up to 100 emails in a single request, significantly improving performance.

Attachments

Resend supports file attachments:

import { sendEmail } from '@/lib/messaging/email';
import { readFileSync } from 'fs';

await sendEmail({
  to: 'user@example.com',
  subject: 'Invoice',
  html: '<p>Please find your invoice attached.</p>',
  attachments: [
    {
      filename: 'invoice.pdf',
      content: readFileSync('./invoice.pdf'),
      contentType: 'application/pdf',
    },
  ],
});

Custom Headers

ShipFree automatically handles unsubscribe headers for marketing emails:

await sendEmail({
  to: 'user@example.com',
  subject: 'Newsletter',
  html: '<p>Monthly newsletter</p>',
  emailType: 'marketing', // Not 'transactional'
  includeUnsubscribe: true,
  unsubscribeInfo: {
    baseUrl: 'https://yourdomain.com',
    token: 'user-token',
    writerId: 'newsletter-id',
  },
});

This automatically adds RFC-compliant List-Unsubscribe headers.

Reply-To Address

await sendEmail({
  to: 'user@example.com',
  subject: 'Support Request',
  html: '<p>Your support ticket</p>',
  replyTo: 'support@yourdomain.com', // Replies go here
});

Environment Variables Reference

Variable	Required	Description	Example
`RESEND_API_KEY`	Yes	Your Resend API key	`re_123abc...`
`RESEND_DOMAIN`	No	Verified sending domain	`mail.yourdomain.com`
`EMAIL_PROVIDER`	No	Force Resend as provider	`resend`
`DEFAULT_FROM_EMAIL`	No	Default sender email	`noreply@yourdomain.com`
`DEFAULT_FROM_NAME`	No	Default sender name	`Your App Name`

Development vs. Production

Development Setup

For development, you can use Resend’s test domain:

# .env.development
RESEND_API_KEY=re_your_test_api_key
DEFAULT_FROM_EMAIL=onboarding@resend.dev
DEFAULT_FROM_NAME=ShipFree Dev

Emails sent from onboarding@resend.dev only deliver to the email address associated with your Resend account. This is perfect for testing but won’t work in production.

Production Setup

# .env.production
RESEND_API_KEY=re_your_production_api_key
RESEND_DOMAIN=mail.yourdomain.com
DEFAULT_FROM_EMAIL=noreply@yourdomain.com
DEFAULT_FROM_NAME=Your App Name

Pricing

Resend offers:

Free Tier: 3,000 emails/month, 100 emails/day
Paid Plans: Starting at $20/month for 50,000 emails
Pay-as-you-go: $1 per 1,000 emails after quota

View current pricing →

Troubleshooting

Error: 'Resend not configured'

This means RESEND_API_KEY is not set or is empty.Solution:

Check your .env file has RESEND_API_KEY=re_...
Restart your development server
Verify the API key is valid in Resend dashboard

Error: 'Invalid from address'

You’re trying to send from an unverified domain.Solution:

For development: Use onboarding@resend.dev
For production: Verify your domain in Resend dashboard
Check DEFAULT_FROM_EMAIL matches your verified domain

Emails not being received

Check these common issues:

Spam folder: Check recipient’s spam/junk folder
Domain verification: Ensure all DNS records are set correctly
API key: Verify it’s a production key, not test key
Rate limits: Check you haven’t exceeded daily/monthly quota
Resend logs: Check the Resend dashboard for delivery status

How do I see sent emails?

View all sent emails in the Resend dashboard:

Log in to resend.com
Go to Emails section
View delivery status, opens, clicks, and more

Each email has a unique ID returned in result.data that you can search for.

Code Reference

The Resend provider implementation is in:

src/lib/messaging/email/providers/resend.ts

Key functions:

createResendProvider() - Initialize provider (line 114)
send() - Send single email (line 27)
sendBatch() - Send batch emails (line 63)

Additional Resources

Resend Documentation

Official Resend API documentation

Resend Dashboard

View sent emails and analytics

React Email

Learn more about React Email templates

Domain Setup

Guide to verifying your domain

Next Steps

Create custom email templates

Learn how to build custom templates in the Email Overview

Test in development

Use the log provider or Resend test domain to test email flows

Monitor delivery

Set up Resend webhooks to track email events (opens, clicks, bounces)

Getting Started

Core Features

Payment Providers

Email Providers

Configuration

Deployment

Overview

Prerequisites

Setup Instructions

Step 1: Get Your API Key

Step 2: Verify Your Domain (Production)

Step 3: Configure Environment Variables

Step 4: Test Your Configuration

Features

Batch Email Support

Attachments

Custom Headers

Reply-To Address

Environment Variables Reference

Development vs. Production

Development Setup

Production Setup

Pricing

Troubleshooting

Code Reference

Additional Resources

Resend Documentation

Resend Dashboard

React Email

Domain Setup

Next Steps

Build docs developers (and LLMs) love

Getting Started

Core Features

Payment Providers

Email Providers

Configuration

Deployment

Documentation Index

​Overview

​Prerequisites

​Setup Instructions

​Step 1: Get Your API Key

​Step 2: Verify Your Domain (Production)

​Step 3: Configure Environment Variables

​Step 4: Test Your Configuration

​Features

​Batch Email Support

​Attachments

​Custom Headers

​Reply-To Address

​Environment Variables Reference

​Development vs. Production

​Development Setup

​Production Setup

​Pricing

​Troubleshooting

​Code Reference

​Additional Resources

Resend Documentation

Resend Dashboard

React Email

Domain Setup

​Next Steps

Build docs developers (and LLMs) love

Overview

Prerequisites

Setup Instructions

Step 1: Get Your API Key

Step 2: Verify Your Domain (Production)

Step 3: Configure Environment Variables

Step 4: Test Your Configuration

Features

Batch Email Support

Attachments

Custom Headers

Reply-To Address

Environment Variables Reference

Development vs. Production

Development Setup

Production Setup

Pricing

Troubleshooting

Code Reference

Additional Resources

Next Steps