Configure email sending with Resend and SMTP for transactional and campaign emails

Email Configuration

Jose Madrid Salsa uses a dual email sending system: Resend as the primary transactional email service and SMTP (via Nodemailer) for campaign emails. The system supports logging, unsubscribe management, and automatic fallback.

Architecture

Email Request
    │
    ├─── React Email Templates (lib/email/client.ts)
    │         └── Renders React components to HTML
    │         └── Sends via Resend with List-Unsubscribe headers
    │
    └─── Campaign / SMTP Emails (lib/email/sender.ts)
              └── Tries SMTP first (from EmailConfiguration in DB)
              └── Falls back to Resend if SMTP fails

Resend (Primary)

The main email client at lib/email.ts and lib/email/client.ts both use the Resend SDK:

lib/email/client.ts

import { Resend } from 'resend'

function getResendClient(): Resend | null {
  const apiKey = process.env.RESEND_API_KEY
  if (!apiKey) return null
  return new Resend(apiKey)
}

Sending with React Templates

The sendEmail function in lib/email/client.ts accepts a React Email component and renders it to HTML:

lib/email/client.ts

export async function sendEmail({
  to,
  subject,
  react,         // React Email component
  from,
  replyTo,
  type,          // Email type for logging/unsubscribe checking
  orderId,
  userId,
}: SendEmailOptions): Promise<EmailSendResult> {
  // Check unsubscribe preferences (skip for transactional emails)
  const isTransactional = ['order-confirmation', 'shipping-notification', 'delivery-confirmation'].includes(type)

  // Render React component to HTML
  const html = await render(react)

  // Send with List-Unsubscribe header for compliance
  const result = await resend.emails.send({
    from,
    to,
    subject,
    html,
    headers: {
      'List-Unsubscribe': `<${unsubscribeUrl}>`,
      'List-Unsubscribe-Post': 'List-Unsubscribe=One-Click',
    },
  })
}

Simple Email Sending

For non-template emails, lib/email.ts provides a simpler interface:

lib/email.ts

export async function sendEmail(options: {
  to: string
  subject: string
  html?: string
  text?: string
}) {
  const resend = new Resend(resendApiKey)
  return resend.emails.send({
    from: fromEmail,
    to: options.to,
    subject: options.subject,
    ...(options.html ? { html: options.html } : { text: options.text }),
  })
}

SMTP (Campaign Emails)

Campaign emails can use database-configured SMTP servers. The lib/email/sender.ts module reads EmailConfiguration records from the database:

lib/email/sender.ts

async function getSMTPTransporter(configId?: string) {
  const config = configId
    ? await prisma.emailConfiguration.findUnique({ where: { id: configId, isActive: true } })
    : await prisma.emailConfiguration.findFirst({ where: { isDefault: true, isActive: true } })

  const decryptedPassword = config.smtpPassword
    ? isEncrypted(config.smtpPassword) ? decrypt(config.smtpPassword) : config.smtpPassword
    : null

  return nodemailer.createTransport({
    host: config.smtpHost,
    port: config.smtpPort || 587,
    secure: port === 465,  // Port 465 = implicit SSL, 587 = STARTTLS
    auth: { user: config.smtpUsername, pass: decryptedPassword },
  })
}

SMTP passwords stored in the database are encrypted with the ENCRYPTION_KEY environment variable using AES-256-GCM. See the Encryption page for details.

Email Sending Priority

When sending via lib/email/sender.ts:

Try SMTP from the database EmailConfiguration (default or specified config)
Fall back to Resend if SMTP fails and useResend is enabled on the config
Fail if neither is available

Campaign Sending

The campaign system sends emails in batches with configurable delays:

lib/email/sender.ts

export async function sendCampaign({
  campaignId,
  batchSize = 50,
  delayBetweenBatches = 1000, // ms
}: CampaignSendOptions)

Processes recipients in parallel batches
Tracks per-recipient status (PENDING, SENDING, SENT, FAILED)
Updates campaign progress after each batch
Supports retry of failed recipients up to maxRetries (default: 3)

Unsubscribe Management

Non-transactional emails check the user's unsubscribe preferences before sending. Transactional emails (order confirmation, shipping notification, delivery confirmation) always send regardless of preferences.

All emails include List-Unsubscribe and List-Unsubscribe-Post headers for one-click unsubscribe compliance.

Required Environment Variables

Variable	Description
`RESEND_API_KEY`	Resend API key (`re_...`)
`FROM_EMAIL`	Default sender address (default: `orders@josemadridsalsa.com`)
`ENCRYPTION_KEY`	Required if using database-stored SMTP passwords

Email Logging

All email sends (successful and failed) are logged to the EmailLog table via lib/email/logger.ts, including:

Recipient (hashed for privacy in logs)
Template ID and subject
Status (SENT or FAILED)
Error message (if failed)
Associated order ID and user ID

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Email Configuration

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