Email Service (Resend)

Email Service (Resend)

This document describes the email service setup for sending transactional emails (e.g., product availability notifications).

Status

Overview

We use Resend as the email sending service. Resend provides a modern API for transactional emails with a generous free tier suitable for our volume.

Why Resend

Configuration

Environment Variables

Domain Setup

The domain takazudomodular.com is verified on Resend with the following DNS records added to Squarespace:

These records use the send subdomain, which avoids conflicts with the existing Mailgun MX records used by Squarespace email forwarding on @.

Email Forwarding (Receiving)

Squarespace email forwarding is configured separately for receiving replies:

This uses the MX records on @ (mxa.mailgun.org, mxb.mailgun.org), which coexist with Resend’s records on the send subdomain.

Usage

Auto-Reply Emails

Auto-reply emails are sent automatically when users submit “Notify Me” or “Reservation” forms. Templates are managed via the zpreorder admin interface.

See netlify/functions/shared/email-templates.ts for the implementation:

import { sendAutoReplyEmail } from './shared/email-templates.js';

await sendAutoReplyEmail({
  templateKey: 'notify',        // or 'reservation'
  to: email,
  variables: {
    PRODUCT_NAME: productName,
    PRODUCT_URL: productUrl ?? 'https://takazudomodular.com',
  },
  logPrefix: 'notify-signup',
});

Available template placeholders:

Single Email Sending

For sending a single email directly (used internally by auto-reply):

import { sendSingleEmail } from './shared/email.js';

const result = await sendSingleEmail(
  'subscriber@example.com',
  'VCO-1 入荷のお知らせ',
  'VCO-1が入荷しました。',
);

Plain text body is automatically converted to HTML with a consistent footer template.

Batch Email Sending (Admin)

The admin-notify-send Netlify Function uses sendEmailBatch() to send product availability notifications to multiple subscribers. See Admin Notify Send for the API specification.

Batch processing details:

• Send emails in batches of 10 to respect rate limits
• 1 second delay between batches
• Track successful/failed sends individually
• Update subscriber status to “notified” after successful send

DNS Architecture

takazudomodular.com DNS (Squarespace)
├── @ (root domain)
│   ├── MX → mxa.mailgun.org (Squarespace email forwarding - RECEIVING)
│   ├── MX → mxb.mailgun.org (Squarespace email forwarding - RECEIVING)
│   ├── TXT → v=spf1 include:mailgun.org ~all (Mailgun SPF)
│   └── TXT → mailo._domainkey DKIM (Mailgun DKIM)
├── send (subdomain)
│   ├── MX → feedback-smtp.ap-northeast-1.amazonses.com (Resend - SENDING)
│   └── TXT → v=spf1 include:amazonses.com ~all (Resend SPF)
├── resend._domainkey
│   └── TXT → DKIM key (Resend domain verification)
└── _dmarc
    └── TXT → v=DMARC1; p=none; (DMARC policy)

Resend Dashboard

• Dashboard: https://resend.com/overview
• API Keys: https://resend.com/api-keys
• Domains: https://resend.com/domains
• Logs: https://resend.com/logs (view sent/failed emails)

Source Files

Related

• Admin Notify Send - API endpoint that triggers batch email sending
• Webhook Notifications - Slack and Discord webhook integration
• Blob Storage - Where notification history and email templates are stored