Resend Email Service Guide

Learn how to set up and automate transactional and marketing emails with Resend, including DNS configuration to avoid spam folders.

Buildfast already includes Resend integration for transactional emails in the Stripe webhook. This guide will help you understand and extend the implementation.

Create a Resend Account

Visit resend.com
Click "Sign up" and create your account
Verify your email address
Complete the onboarding process
You'll receive 3,000 free emails per month on the free tier

Get Your API Key

Generate and configure your Resend API key

1. Navigate to API Keys

In your Resend dashboard, go to API Keys

2. Create API Key

Click "Create API Key"
Name: "Production" (or your preferred name)
Permission: "Full Access" for transactional emails
Click "Create"

3. Copy Your API Key

Copy and save your API key immediately. You won't be able to see it again!

Existing Buildfast Integration

Buildfast already uses Resend for transactional emails

1. Resend Instance

The Resend client is initialized in lib/resend.ts:

import { Resend } from 'resend'; export const resend = new Resend(process.env.RESEND_API_KEY);

2. Webhook Integration

Transactional emails are sent from the Stripe webhook when a payment is processed:

Located in app/api/webhooks/route.ts
Sends payment confirmation emails
Uses React Email templates for beautiful HTML emails
Handles different payment statuses

3. React Email Template

The email template is in emails/vercel-email.tsx and includes:

Company logo
Dynamic headings based on payment status
Formatted payment amounts
Professional email layout

Environment Variables

Configure your Resend API key

Add to your .env file:

# Resend Configuration
RESEND_API_KEY=re_XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

Your Resend client is already configured in lib/resend.ts and ready to use throughout your application.

DNS Configuration (Avoid Spam Folders)

Set up DKIM, SPF, and DMARC to improve email deliverability

1. Add Your Domain to Resend

Go to Domains in your Resend dashboard
Click "Add Domain"
Enter your domain (e.g., yourdomain.com)
Click "Add"

2. Configure DNS Records

Add these records to your DNS provider (e.g., Vercel Domains):

SPF Record:

TXT @ "v=spf1 include:amazonses.com ~all"

DKIM Records (3 CNAME records):

resend._domainkey → resend._domainkey.yourdomain.com.dkim.amazonses.com
resend2._domainkey → resend2._domainkey.yourdomain.com.dkim.amazonses.com
resend3._domainkey → resend3._domainkey.yourdomain.com.dkim.amazonses.com

DMARC Record (Optional but recommended):

TXT _dmarc "v=DMARC1; p=none; rua=mailto:dmarc@yourdomain.com"

3. Verify Domain

Return to Resend dashboard
Click "Verify DNS records"
Wait for all records to show green checkmarks
DNS propagation can take up to 48 hours

Sending Emails

Examples of sending transactional and marketing emails

1. Basic Email

await resend.emails.send({ from: 'Your App <noreply@yourdomain.com>', to: 'user@example.com', subject: 'Welcome to Our App!', html: '<p>Thanks for signing up!</p>' });

2. React Email Template

import { WelcomeEmail } from '@/emails/welcome'; await resend.emails.send({ from: 'Your App <noreply@yourdomain.com>', to: user.email, subject: 'Welcome aboard!', react: WelcomeEmail({ username: user.name, loginUrl: 'https://app.yourdomain.com/login' }) });

3. Batch Emails (Marketing)

await resend.batch.send([ { from: 'Newsletter <news@yourdomain.com>', to: 'subscriber1@example.com', subject: 'Monthly Update', react: NewsletterEmail({ name: 'John' }) }, { from: 'Newsletter <news@yourdomain.com>', to: 'subscriber2@example.com', subject: 'Monthly Update', react: NewsletterEmail({ name: 'Jane' }) } ]);

Best Practices

Tips for better email deliverability and user experience

Use a subdomain for transactional emails

e.g., noreply@mail.yourdomain.com

Always include an unsubscribe link

Required for marketing emails, good practice for all

Test emails before sending

Use Resend's test mode or send to yourself first

Monitor your sender reputation

Check bounce rates and spam complaints regularly

Use React Email for consistent templates

Ensures emails look great across all clients

Test Your Integration

Verify email sending is working

Start your development server:pnpm dev
Make a test purchase through Stripe Checkout
Check your email for the payment confirmation
Verify the email arrives and displays correctly
Check Resend dashboard for email logs and status
Monitor for any bounce backs or delivery issues

For production, ensure your DNS records are verified and consider upgrading to a paid Resend plan for higher sending limits and better deliverability features.

Documentation