Email Setup Command

<command_purpose> Guide developers through complete Resend email integration with automated code generation, React Email templates, domain configuration, and MCP-driven email setup. </command_purpose>

Introduction

<role>Senior Email Integration Engineer with expertise in Resend, React Email, and Cloudflare Workers email delivery</role>

This command will:

Detect project type (Tanstack Start or API-only Worker)
Install Resend SDK and React Email dependencies
Generate React Email template components
Create email server functions for Tanstack Start
Configure transactional email handlers (verification, password reset)
Generate marketing email examples (newsletter)
Set up domain verification configuration
Configure environment variables and secrets
Add error handling and retry logic with D1

Prerequisites

<requirements> - Cloudflare Workers project (Tanstack Start or Hono) - Resend account: https://resend.com (free tier available) - API key from Resend dashboard - D1 database configured for email retry tracking (optional) </requirements>

Main Tasks

1. Detect Project Type & Email Requirements

Ask User:

📧 Email Setup Wizard

1. What project type are you using?
   a) Tanstack Start (full-stack)
   b) Standalone Worker (Hono/plain TS)

2. What email flows do you need?
   a) Transactional only (verification, password reset)
   b) Marketing only (newsletters, announcements)
   c) Both transactional and marketing
   d) Custom email patterns

Decision Logic:

If Tanstack Start + Any type:
  → Use createServerFn for email handlers
  → Generate React Email templates
  → Use @react-email/components

If Standalone Worker:
  → Use Worker handlers
  → Generate React Email templates
  → Use @react-email/components

2. Install Dependencies

For Tanstack Start:

npm install resend @react-email/components @react-email/render
npm install -D @types/react @types/react-dom

For Standalone Worker:

npm install resend @react-email/components @react-email/render
npm install -D @types/react @types/react-dom

React Email Setup:

# Add React Email CLI (optional, for preview server)
npm install -D react-email

3. Generate React Email Templates

Template: Email Verification

Generate File: emails/verify-email.tsx

import {
  Body,
  Button,
  Container,
  Head,
  Heading,
  Html,
  Link,
  Preview,
  Section,
  Text,
} from '@react-email/components';

interface VerifyEmailProps {
  verificationUrl: string;
  email: string;
}

const baseUrl = process.env.RESEND_BASE_URL || 'https://example.com';

export function VerifyEmail({ verificationUrl, email }: VerifyEmailProps) {
  return (
    <Html>
      <Head />
      <Preview>Verify your email address</Preview>
      <Body style={main}>
        <Container style={container}>
          <Section style={box}>
            <Heading style={heading}>Verify your email</Heading>
            <Text style={paragraph}>
              Thanks for signing up! Please verify your email address to complete your registration.
            </Text>
            <Button style={button} href={verificationUrl}>
              Verify Email
            </Button>
            <Text style={paragraph}>
              Or copy and paste this link:
            </Text>
            <Link style={link} href={verificationUrl}>
              {verificationUrl}
            </Link>
            <Text style={paragraph}>
              This link expires in 24 hours. If you didn't create this account, you can safely ignore this email.
            </Text>
          </Section>
          <Text style={footer}>
            © 2025 Your Company. All rights reserved.
          </Text>
        </Container>
      </Body>
    </Html>
  );
}

// Styles
const main = {
  backgroundColor: '#f6f9fc',
  fontFamily:
    '-apple-system,BlinkMacSystemFont,"Segoe UI","Roboto","Oxygen-Sans",Ubuntu,Cantarell,"Helvetica Neue",sans-serif',
};

const container = {
  backgroundColor: '#ffffff',
  margin: '0 auto',
  padding: '20px 0 48px',
  marginBottom: '64px',
};

const box = {
  padding: '0 48px',
};

const heading = {
  color: '#1f2937',
  fontSize: '24px',
  fontWeight: 'bold',
  margin: '16px 0',
};

const paragraph = {
  color: '#525252',
  fontSize: '16px',
  lineHeight: '26px',
  margin: '16px 0',
};

const button = {
  backgroundColor: '#000000',
  borderRadius: '4px',
  color: '#fff',
  fontSize: '16px',
  fontWeight: 'bold',
  textDecoration: 'none',
  textAlign: 'center' as const,
  display: 'block',
  padding: '12px 20px',
  margin: '16px 0',
};

const link = {
  color: '#0000ee',
  textDecoration: 'underline',
};

const footer = {
  color: '#8898aa',
  fontSize: '12px',
  margin: '16px 0',
};

Template: Password Reset

Generate File: emails/password-reset.tsx

import {
  Body,
  Button,
  Container,
  Head,
  Heading,
  Html,
  Link,
  Preview,
  Section,
  Text,
} from '@react-email/components';

interface PasswordResetProps {
  resetUrl: string;
  email: string;
}

export function PasswordReset({ resetUrl, email }: PasswordResetProps) {
  return (
    <Html>
      <Head />
      <Preview>Reset your password</Preview>
      <Body style={main}>
        <Container style={container}>
          <Section style={box}>
            <Heading style={heading}>Reset your password</Heading>
            <Text style={paragraph}>
              We received a request to reset your password. Click the button below to create a new password.
            </Text>
            <Button style={button} href={resetUrl}>
              Reset Password
            </Button>
            <Text style={paragraph}>
              Or copy and paste this link:
            </Text>
            <Link style={link} href={resetUrl}>
              {resetUrl}
            </Link>
            <Text style={paragraph}>
              This link expires in 1 hour. If you didn't request a password reset, you can safely ignore this email.
            </Text>
            <Text style={hint}>
              For security, never share this link with anyone.
            </Text>
          </Section>
          <Text style={footer}>
            © 2025 Your Company. All rights reserved.
          </Text>
        </Container>
      </Body>
    </Html>
  );
}

// Styles (same as VerifyEmail)
const main = {
  backgroundColor: '#f6f9fc',
  fontFamily:
    '-apple-system,BlinkMacSystemFont,"Segoe UI","Roboto","Oxygen-Sans",Ubuntu,Cantarell,"Helvetica Neue",sans-serif',
};

const container = {
  backgroundColor: '#ffffff',
  margin: '0 auto',
  padding: '20px 0 48px',
  marginBottom: '64px',
};

const box = {
  padding: '0 48px',
};

const heading = {
  color: '#1f2937',
  fontSize: '24px',
  fontWeight: 'bold',
  margin: '16px 0',
};

const paragraph = {
  color: '#525252',
  fontSize: '16px',
  lineHeight: '26px',
  margin: '16px 0',
};

const hint = {
  color: '#f59e0b',
  fontSize: '14px',
  fontStyle: 'italic',
  margin: '16px 0',
};

const button = {
  backgroundColor: '#000000',
  borderRadius: '4px',
  color: '#fff',
  fontSize: '16px',
  fontWeight: 'bold',
  textDecoration: 'none',
  textAlign: 'center' as const,
  display: 'block',
  padding: '12px 20px',
  margin: '16px 0',
};

const link = {
  color: '#0000ee',
  textDecoration: 'underline',
};

const footer = {
  color: '#8898aa',
  fontSize: '12px',
  margin: '16px 0',
};

Template: Newsletter

Generate File: emails/newsletter.tsx

import {
  Body,
  Button,
  Container,
  Head,
  Heading,
  Html,
  Link,
  Preview,
  Section,
  Text,
} from '@react-email/components';

interface NewsletterProps {
  month: string;
  articles: Array<{
    title: string;
    description: string;
    url: string;
  }>;
  unsubscribeUrl: string;
}

export function Newsletter({ month, articles, unsubscribeUrl }: NewsletterProps) {
  return (
    <Html>
      <Head />
      <Preview>{month} Newsletter - Latest updates</Preview>
      <Body style={main}>
        <Container style={container}>
          <Section style={header}>
            <Heading style={heading}>{month} Newsletter</Heading>
            <Text style={subtitle}>Your monthly roundup of updates and insights</Text>
          </Section>

          {articles.map((article, index) => (
            <Section key={index} style={articleSection}>
              <Heading style={articleHeading}>{article.title}</Heading>
              <Text style={paragraph}>{article.description}</Text>
              <Button style={button} href={article.url}>
                Read More
              </Button>
            </Section>
          ))}

          <Section style={footer}>
            <Text style={footerText}>
              © 2025 Your Company. All rights reserved.
            </Text>
            <Link style={unsubscribeLink} href={unsubscribeUrl}>
              Unsubscribe
            </Link>
          </Section>
        </Container>
      </Body>
    </Html>
  );
}

// Styles
const main = {
  backgroundColor: '#f6f9fc',
  fontFamily:
    '-apple-system,BlinkMacSystemFont,"Segoe UI","Roboto","Oxygen-Sans",Ubuntu,Cantarell,"Helvetica Neue",sans-serif',
};

const container = {
  backgroundColor: '#ffffff',
  margin: '0 auto',
  padding: '48px 0',
  marginBottom: '64px',
};

const header = {
  backgroundColor: '#000000',
  padding: '32px 48px',
};

const heading = {
  color: '#ffffff',
  fontSize: '32px',
  fontWeight: 'bold',
  margin: '0',
};

const subtitle = {
  color: '#cccccc',
  fontSize: '16px',
  margin: '8px 0 0 0',
};

const articleSection = {
  padding: '32px 48px',
  borderBottom: '1px solid #e5e7eb',
};

const articleHeading = {
  color: '#1f2937',
  fontSize: '20px',
  fontWeight: 'bold',
  margin: '0 0 16px 0',
};

const paragraph = {
  color: '#525252',
  fontSize: '16px',
  lineHeight: '26px',
  margin: '16px 0',
};

const button = {
  backgroundColor: '#000000',
  borderRadius: '4px',
  color: '#fff',
  fontSize: '16px',
  fontWeight: 'bold',
  textDecoration: 'none',
  textAlign: 'center' as const,
  display: 'inline-block',
  padding: '12px 20px',
  margin: '16px 0',
};

const footer = {
  padding: '32px 48px',
};

const footerText = {
  color: '#8898aa',
  fontSize: '12px',
  margin: '0 0 16px 0',
};

const unsubscribeLink = {
  color: '#8898aa',
  fontSize: '12px',
  textDecoration: 'underline',
};

4. Generate Email Server Functions (Tanstack Start)

Generate File: server/emails/send-verify-email.ts

import { createServerFn } from '@tanstack/start';
import { Resend } from 'resend';
import { VerifyEmail } from '@/emails/verify-email';

interface SendVerifyEmailInput {
  to: string;
  verificationUrl: string;
}

export const sendVerifyEmail = createServerFn(
  'POST',
  async (input: SendVerifyEmailInput, context) => {
    const { env } = context.cloudflare;
    const resend = new Resend(env.RESEND_API_KEY);

    try {
      const { data, error } = await resend.emails.send({
        from: 'noreply@yourdomain.com',
        to: input.to,
        subject: 'Verify your email address',
        react: VerifyEmail({
          verificationUrl: input.verificationUrl,
          email: input.to,
        }),
      });

      if (error) {
        console.error('Resend error:', error);
        throw new Error(`Failed to send verification email: ${error.message}`);
      }

      // Log sent email for audit trail
      if (env.DB) {
        await env.DB.prepare(
          `INSERT INTO sent_emails (id, to, subject, type, email_id, created_at)
           VALUES (?, ?, ?, ?, ?, ?)`
        ).bind(
          crypto.randomUUID(),
          input.to,
          'Verify your email address',
          'verification',
          data.id,
          new Date().toISOString()
        ).run();
      }

      return { success: true, emailId: data.id };
    } catch (error) {
      console.error('Email send error:', error);

      // Store failed email for retry
      if (env.DB) {
        await env.DB.prepare(
          `INSERT INTO failed_emails (id, to, subject, type, error, created_at)
           VALUES (?, ?, ?, ?, ?, ?)`
        ).bind(
          crypto.randomUUID(),
          input.to,
          'Verify your email address',
          'verification',
          error instanceof Error ? error.message : 'Unknown error',
          new Date().toISOString()
        ).run();
      }

      return {
        success: false,
        error: 'Email delivery failed. Please try again later.',
      };
    }
  }
);

Generate File: server/emails/send-password-reset.ts

import { createServerFn } from '@tanstack/start';
import { Resend } from 'resend';
import { PasswordReset } from '@/emails/password-reset';

interface SendPasswordResetInput {
  to: string;
  resetUrl: string;
}

export const sendPasswordReset = createServerFn(
  'POST',
  async (input: SendPasswordResetInput, context) => {
    const { env } = context.cloudflare;
    const resend = new Resend(env.RESEND_API_KEY);

    try {
      const { data, error } = await resend.emails.send({
        from: 'noreply@yourdomain.com',
        to: input.to,
        subject: 'Reset your password',
        react: PasswordReset({
          resetUrl: input.resetUrl,
          email: input.to,
        }),
      });

      if (error) {
        console.error('Resend error:', error);
        throw new Error(`Failed to send password reset email: ${error.message}`);
      }

      // Log sent email
      if (env.DB) {
        await env.DB.prepare(
          `INSERT INTO sent_emails (id, to, subject, type, email_id, created_at)
           VALUES (?, ?, ?, ?, ?, ?)`
        ).bind(
          crypto.randomUUID(),
          input.to,
          'Reset your password',
          'password_reset',
          data.id,
          new Date().toISOString()
        ).run();
      }

      return { success: true, emailId: data.id };
    } catch (error) {
      console.error('Email send error:', error);

      // Store failed email for retry
      if (env.DB) {
        await env.DB.prepare(
          `INSERT INTO failed_emails (id, to, subject, type, error, created_at)
           VALUES (?, ?, ?, ?, ?, ?)`
        ).bind(
          crypto.randomUUID(),
          input.to,
          'Reset your password',
          'password_reset',
          error instanceof Error ? error.message : 'Unknown error',
          new Date().toISOString()
        ).run();
      }

      return {
        success: false,
        error: 'Email delivery failed. Please try again later.',
      };
    }
  }
);

Generate File: server/emails/send-newsletter.ts

import { createServerFn } from '@tanstack/start';
import { Resend } from 'resend';
import { Newsletter } from '@/emails/newsletter';

interface NewsletterArticle {
  title: string;
  description: string;
  url: string;
}

interface SendNewsletterInput {
  to: string[];
  month: string;
  articles: NewsletterArticle[];
  unsubscribeBaseUrl: string;
}

export const sendNewsletter = createServerFn(
  'POST',
  async (input: SendNewsletterInput, context) => {
    const { env } = context.cloudflare;
    const resend = new Resend(env.RESEND_API_KEY);

    try {
      // Batch send using Resend's batch API
      const batch = input.to.map(email => ({
        from: 'newsletter@yourdomain.com',
        to: email,
        subject: `${input.month} Newsletter - Latest updates`,
        react: Newsletter({
          month: input.month,
          articles: input.articles,
          unsubscribeUrl: `${input.unsubscribeBaseUrl}?email=${encodeURIComponent(email)}`,
        }),
      }));

      const { data, error } = await resend.batch.send(batch);

      if (error) {
        console.error('Batch send error:', error);
        throw new Error(`Failed to send newsletters: ${error.message}`);
      }

      // Log sent emails
      if (env.DB) {
        for (const email of input.to) {
          await env.DB.prepare(
            `INSERT INTO sent_emails (id, to, subject, type, email_id, created_at)
             VALUES (?, ?, ?, ?, ?, ?)`
          ).bind(
            crypto.randomUUID(),
            email,
            `${input.month} Newsletter`,
            'newsletter',
            data?.id || 'batch',
            new Date().toISOString()
          ).run();
        }
      }

      return {
        success: true,
        sent: input.to.length,
        batchId: data?.id,
      };
    } catch (error) {
      console.error('Newsletter send error:', error);

      // Store failed batch
      if (env.DB) {
        for (const email of input.to) {
          await env.DB.prepare(
            `INSERT INTO failed_emails (id, to, subject, type, error, created_at)
             VALUES (?, ?, ?, ?, ?, ?)`
          ).bind(
            crypto.randomUUID(),
            email,
            `${input.month} Newsletter`,
            'newsletter',
            error instanceof Error ? error.message : 'Unknown error',
            new Date().toISOString()
          ).run();
        }
      }

      return {
        success: false,
        error: 'Newsletter delivery failed. Please try again later.',
      };
    }
  }
);

5. Generate Database Migration for Email Tracking

Generate File: migrations/0001_email_tracking.sql

-- Sent emails log (audit trail)
CREATE TABLE sent_emails (
  id TEXT PRIMARY KEY,
  to TEXT NOT NULL,
  subject TEXT NOT NULL,
  type TEXT NOT NULL, -- 'verification', 'password_reset', 'newsletter', 'custom'
  email_id TEXT UNIQUE, -- Resend email ID for tracking
  opened INTEGER DEFAULT 0,
  clicked INTEGER DEFAULT 0,
  bounced INTEGER DEFAULT 0,
  created_at TEXT NOT NULL,
  updated_at TEXT NOT NULL
);

-- Failed emails for retry logic
CREATE TABLE failed_emails (
  id TEXT PRIMARY KEY,
  to TEXT NOT NULL,
  subject TEXT NOT NULL,
  type TEXT NOT NULL,
  error TEXT,
  retry_count INTEGER DEFAULT 0,
  last_retry_at TEXT,
  created_at TEXT NOT NULL
);

-- Indexes for performance
CREATE INDEX idx_sent_emails_to ON sent_emails(to);
CREATE INDEX idx_sent_emails_type ON sent_emails(type);
CREATE INDEX idx_sent_emails_created ON sent_emails(created_at);
CREATE INDEX idx_failed_emails_to ON failed_emails(to);
CREATE INDEX idx_failed_emails_type ON failed_emails(type);
CREATE INDEX idx_failed_emails_retry_count ON failed_emails(retry_count);

Run Migration:

wrangler d1 migrations apply DB --local
wrangler d1 migrations apply DB --remote

6. Configure Environment Variables

Update: wrangler.toml

# Add Resend API key binding
[env.production.vars]
# RESEND_API_KEY should be set as a secret, not in this file

# D1 database binding (if using email tracking)
[[d1_databases]]
binding = "DB"
database_name = "my-app-db"
database_id = "..."  # Get from: wrangler d1 create my-app-db

Create: .dev.vars (local development)

# Resend API Key (sensitive - DO NOT COMMIT)
RESEND_API_KEY=re_your_api_key_here

# Your domain for email sender (update to your domain)
# RESEND_FROM_EMAIL=noreply@yourdomain.com

Production Setup:

# Set Resend API key as a secret
wrangler secret put RESEND_API_KEY
# Paste: re_xxxxxxxxxxxxx

7. Configure Domain Verification

Instructions for User:

## Setup Custom Email Domain (Required for Production)

### Step 1: Add Domain in Resend
1. Go to https://resend.com/dashboard/domains
2. Click "Add Domain"
3. Enter your domain (e.g., yourdomain.com)
4. Resend will show DNS records to add

### Step 2: Add DNS Records
Add these records to your domain's DNS provider (Cloudflare, Route53, etc.):

**SPF Record**:

Type: TXT Name: yourdomain.com Value: v=spf1 include:resend.com ~all


**DKIM Record**:

Type: CNAME Name: default._domainkey.yourdomain.com Value: [value from Resend dashboard]


**DMARC Record** (optional but recommended):

Type: TXT Name: _dmarc.yourdomain.com Value: v=DMARC1; p=quarantine; rua=mailto:dmarc@yourdomain.com


### Step 3: Verify Domain
1. Return to Resend dashboard
2. Click "Verify Domain"
3. Wait for DNS propagation (usually 5-30 minutes)
4. Once verified, use `from: 'noreply@yourdomain.com'` in emails

### Step 4: Update Email Templates
Replace `noreply@yourdomain.com` with your verified domain across all email functions.

### Development
For development/testing only, use:

from: 'onboarding@resend.dev'

This works without domain verification but is limited to emails you've verified with Resend.

8. Setup Email Retry Logic

Generate File: server/utils/email-retry.ts

import { Resend } from 'resend';

interface Env {
  RESEND_API_KEY: string;
  DB: D1Database;
}

export async function retryFailedEmails(env: Env) {
  const resend = new Resend(env.RESEND_API_KEY);

  // Get failed emails that haven't exceeded retry limit
  const failed = await env.DB.prepare(
    `SELECT * FROM failed_emails
     WHERE retry_count < 3
     AND (last_retry_at IS NULL OR datetime(last_retry_at) < datetime('now', '-1 hour'))
     LIMIT 10`
  ).all();

  if (!failed.results || failed.results.length === 0) {
    console.log('No emails to retry');
    return { retried: 0, succeeded: 0, failed: 0 };
  }

  let succeeded = 0;
  let retryFailed = 0;

  for (const email of failed.results) {
    try {
      // Reconstruct and resend based on type
      // This is a simplified version - you may need to store template data
      const { error } = await resend.emails.send({
        from: 'noreply@yourdomain.com',
        to: email.to,
        subject: email.subject,
        html: `<p>Retry: ${email.subject}</p>`,
      });

      if (error) {
        // Increment retry count and update last_retry_at
        await env.DB.prepare(
          `UPDATE failed_emails
           SET retry_count = retry_count + 1,
               last_retry_at = ?
           WHERE id = ?`
        ).bind(new Date().toISOString(), email.id).run();

        retryFailed++;
      } else {
        // Move to sent_emails and remove from failed_emails
        await env.DB.prepare(
          `DELETE FROM failed_emails WHERE id = ?`
        ).bind(email.id).run();

        succeeded++;
      }
    } catch (error) {
      console.error('Retry error for email:', email.id, error);
      retryFailed++;
    }
  }

  return {
    retried: failed.results.length,
    succeeded,
    failed: retryFailed,
  };
}

Setup Scheduled Retry (using Cloudflare Cron):

Update wrangler.toml:

[[triggers.crons]]
crons = ["0 */6 * * *"]  # Run every 6 hours

Create src/scheduled.ts:

export default {
  async scheduled(event: ScheduledEvent, env: Env, ctx: ExecutionContext) {
    ctx.waitUntil(
      (async () => {
        const result = await retryFailedEmails(env);
        console.log('Email retry results:', result);
      })()
    );
  },
};

9. Integrate with Authentication

Example: Send verification email on signup

Update server/routes/auth/register.ts:

import { sendVerifyEmail } from '@/server/emails/send-verify-email';

export default defineEventHandler(async (event) => {
  const { email, password } = await readBody(event);

  // Create user...
  const user = await createUser(email, password, event.context.cloudflare.env.DB);

  // Generate verification token
  const token = generateToken(user.id);

  // Send verification email
  const verifyUrl = `${process.env.PUBLIC_URL}/verify?token=${token}`;
  await sendVerifyEmail({
    to: email,
    verificationUrl: verifyUrl,
  });

  return {
    success: true,
    message: 'Account created. Please check your email to verify.',
  };
});

Example: Send password reset email

Create server/routes/auth/forgot-password.ts:

import { sendPasswordReset } from '@/server/emails/send-password-reset';

export default defineEventHandler(async (event) => {
  const { email } = await readBody(event);

  // Find user
  const user = await findUserByEmail(email, event.context.cloudflare.env.DB);

  if (!user) {
    // Don't reveal if email exists (security)
    return {
      success: true,
      message: 'If an account exists, a reset link has been sent.',
    };
  }

  // Generate reset token
  const token = generateToken(user.id, '1h');

  // Send password reset email
  const resetUrl = `${process.env.PUBLIC_URL}/reset-password?token=${token}`;
  await sendPasswordReset({
    to: email,
    resetUrl,
  });

  return {
    success: true,
    message: 'Password reset email sent.',
  };
});

10. Setup Email Analytics Webhook (Optional)

Resend Webhook Configuration:

Go to https://resend.com/dashboard/settings/webhooks
Add webhook endpoint: https://yourdomain.com/api/webhooks/email
Subscribe to events:
- email.sent
- email.opened
- email.clicked
- email.bounced

Create Handler: server/api/webhooks/email.ts

export default defineEventHandler(async (event) => {
  const body = await readBody(event);
  const { type, data } = body;

  try {
    switch (type) {
      case 'email.sent':
        await updateEmailStatus(data.email_id, 'sent', event.context.cloudflare.env.DB);
        break;

      case 'email.opened':
        await updateEmailStatus(data.email_id, 'opened', event.context.cloudflare.env.DB);
        break;

      case 'email.clicked':
        await updateEmailStatus(data.email_id, 'clicked', event.context.cloudflare.env.DB);
        break;

      case 'email.bounced':
        await handleBounce(data.email_id, data.email, event.context.cloudflare.env.DB);
        break;

      default:
        console.log('Unknown email event:', type);
    }

    return { success: true };
  } catch (error) {
    console.error('Webhook error:', error);
    return { success: false, error: String(error) };
  }
});

async function updateEmailStatus(emailId: string, status: string, db: D1Database) {
  await db.prepare(
    `UPDATE sent_emails SET ${status} = 1, updated_at = ? WHERE email_id = ?`
  ).bind(new Date().toISOString(), emailId).run();
}

async function handleBounce(emailId: string, email: string, db: D1Database) {
  await db.prepare(
    `UPDATE sent_emails SET bounced = 1, updated_at = ? WHERE email_id = ?`
  ).bind(new Date().toISOString(), emailId).run();

  // Optionally mark email as invalid for future use
  // await db.prepare(
  //   `INSERT INTO invalid_emails (email) VALUES (?) ON CONFLICT DO NOTHING`
  // ).bind(email).run();
}

11. Testing Email Flows

Test Email Sending:

// Use Resend's test address
const { data, error } = await resend.emails.send({
  from: 'test@yourdomain.com',
  to: 'test@resend.dev', // Special test address
  subject: 'Test email',
  react: VerifyEmail({
    verificationUrl: 'https://example.com/verify?token=test',
    email: 'test@resend.dev',
  }),
});

Playwright E2E Test Example:

test('sends verification email on signup', async ({ page }) => {
  await page.goto('/signup');

  await page.fill('[name="email"]', 'test@example.com');
  await page.fill('[name="password"]', 'Test123!@#');
  await page.click('button[type="submit"]');

  // Verify success message
  await expect(page.locator('[data-testid="success-message"]'))
    .toContainText('Check your email');

  // In real scenario, verify email was sent via Resend API
  // This test verifies the UI flow, not actual email delivery
});

Preview React Email Templates:

# Start React Email preview server
npm run email:preview

# Open http://localhost:3000 to preview templates

Success Criteria

✅ Email setup complete when:

Resend SDK and React Email dependencies installed
All email templates generated (verification, password reset, newsletter)
Server functions created for sending emails
Database migration for email tracking
Environment variables configured
Domain verification setup (at least documented)
Error handling and retry logic implemented
Integration with auth flows completed
Email previews working
Testing strategy documented

Output Summary

Files Created:

Email templates:
- emails/verify-email.tsx
- emails/password-reset.tsx
- emails/newsletter.tsx
Server functions:
- server/emails/send-verify-email.ts
- server/emails/send-password-reset.ts
- server/emails/send-newsletter.ts
Database migration: migrations/0001_email_tracking.sql
Utilities: server/utils/email-retry.ts
Webhook handler: server/api/webhooks/email.ts
Scheduled job: src/scheduled.ts

Files Updated:

wrangler.toml (Resend vars, D1 binding)
.dev.vars (template)

Next Actions:

Install dependencies: npm install resend @react-email/components
Run database migration: wrangler d1 migrations apply DB
Generate Resend API key: https://resend.com/dashboard
Add to secrets: wrangler secret put RESEND_API_KEY
Configure domain in Resend dashboard
Test email flows with signup
Preview templates: npm run email:preview
Deploy with /es-deploy

Notes

Always use Resend for transactional and marketing emails
React Email provides type-safe, component-based templates
Store RESEND_API_KEY as Cloudflare secret (not in wrangler.toml)
Domain verification required for production (use onboarding@resend.dev for testing)
Email retry logic handles transient failures
Track email opens/clicks via Resend webhooks
Test with onboarding@resend.dev before using custom domain
Use batch API for newsletters to multiple recipients
See agents/integrations/resend-email-specialist for detailed guidance

/es-email-setup