Email Template Builder

Email Template Builder

brathod1432 1b2f539 2 files · 15.5 KB Updated Sep 17, 2026

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Internal Safety Override

Status: local-only unless explicitly opted into external access.
Before using network tools, account connectors, browser automation, or APIs, state the destination, data scope, and credential source.
Do not transmit repository files, secrets, credentials, or private documents by default.
Audit categories: network, secrets.

Email Template Builder

Tier: POWERFUL
Category: Engineering Team
Domain: Transactional Email / Communications Infrastructure

Overview

Build complete transactional email systems: React Email templates, provider integration, preview server, i18n support, dark mode, spam optimization, and analytics tracking. Output production-ready code for Resend, Postmark, SendGrid, or AWS SES.

Core Capabilities

React Email templates (welcome, verification, password reset, invoice, notification, digest)
MJML templates for maximum email client compatibility
Multi-provider support with unified sending interface
Local preview server with hot reload
i18n/localization with typed translation keys
Dark mode support using media queries
Spam score optimization checklist
Open/click tracking with UTM parameters

When to Use

Setting up transactional email for a new product
Migrating from a legacy email system
Adding new email types (invoice, digest, notification)
Debugging email deliverability issues
Implementing i18n for email templates

Project Structure

emails/
├── components/
│   ├── layout/
│   │   ├── email-layout.tsx       # Base layout with brand header/footer
│   │   └── email-button.tsx       # CTA button component
│   ├── partials/
│   │   ├── header.tsx
│   │   └── footer.tsx
├── templates/
│   ├── welcome.tsx
│   ├── verify-email.tsx
│   ├── password-reset.tsx
│   ├── invoice.tsx
│   ├── notification.tsx
│   └── weekly-digest.tsx
├── lib/
│   ├── send.ts                    # Unified send function
│   ├── providers/
│   │   ├── resend.ts
│   │   ├── postmark.ts
│   │   └── ses.ts
│   └── tracking.ts                # UTM + analytics
├── i18n/
│   ├── en.ts
│   └── de.ts
└── preview/                       # Dev preview server
    └── server.ts

Base Email Layout

// emails/components/layout/email-layout.tsx
import {
  Body, Container, Head, Html, Img, Preview, Section, Text, Hr, Font
} from "@react-email/components"

interface EmailLayoutProps {
  preview: string
  children: React.ReactNode
}

export function EmailLayout({ preview, children }: EmailLayoutProps) {
  return (
    <Html lang="en">
      <Head>
        <Font
          fontFamily="Inter"
          fallbackFontFamily="Arial"
          webFont={{ url: "https://fonts.gstatic.com/s/inter/v13/UcCO3FwrK3iLTeHuS_nVMrMxCp50SjIw2boKoduKmMEVuLyfAZ9hiJ-Ek-_EeA.woff2", format: "woff2" }}
          fontWeight={400}
          fontStyle="normal"
        />
        {/* Dark mode styles */}
        <style>{`
          @media (prefers-color-scheme: dark) {
            .email-body { background-color: #0f0f0f !important; }
            .email-container { background-color: #1a1a1a !important; }
            .email-text { color: #e5e5e5 !important; }
            .email-heading { color: #ffffff !important; }
            .email-divider { border-color: #333333 !important; }
          }
        `}</style>
      </Head>
      <Preview>{preview}</Preview>
      <Body className="email-body" style={styles.body}>
        <Container className="email-container" style={styles.container}>
          {/* Header */}
          <Section style={styles.header}>
            <Img src="https://yourapp.com/logo.png" width={120} height={40} alt="MyApp" />
          </Section>
          
          {/* Content */}
          <Section style={styles.content}>
            {children}
          </Section>
          
          {/* Footer */}
          <Hr style={styles.divider} />
          <Section style={styles.footer}>
            <Text style={styles.footerText}>
              MyApp Inc. · 123 Main St · San Francisco, CA 94105
            </Text>
            <Text style={styles.footerText}>
              <a href="{{unsubscribe_url}}" style={styles.link}>Unsubscribe</a>
              {" · "}
              <a href="https://yourapp.com/privacy" style={styles.link}>Privacy Policy</a>
            </Text>
          </Section>
        </Container>
      </Body>
    </Html>
  )
}

const styles = {
  body: { backgroundColor: "#f5f5f5", fontFamily: "Inter, Arial, sans-serif" },
  container: { maxWidth: "600px", margin: "0 auto", backgroundColor: "#ffffff", borderRadius: "8px", overflow: "hidden" },
  header: { padding: "24px 32px", borderBottom: "1px solid #e5e5e5" },
  content: { padding: "32px" },
  divider: { borderColor: "#e5e5e5", margin: "0 32px" },
  footer: { padding: "24px 32px" },
  footerText: { fontSize: "12px", color: "#6b7280", textAlign: "center" as const, margin: "4px 0" },
  link: { color: "#6b7280", textDecoration: "underline" },
}

Welcome Email

// emails/templates/welcome.tsx
import { Button, Heading, Text } from "@react-email/components"
import { EmailLayout } from "../components/layout/email-layout"

interface WelcomeEmailProps {
  name: "string"
  confirmUrl: string
  trialDays?: number
}

export function WelcomeEmail({ name, confirmUrl, trialDays = 14 }: WelcomeEmailProps) {
  return (
    <EmailLayout preview={`Welcome to MyApp, ${name}! Confirm your email to get started.`}>
      <Heading style={styles.h1}>Welcome to MyApp, {name}!</Heading>
      <Text style={styles.text}>
        We're excited to have you on board. You've got {trialDays} days to explore everything MyApp has to offer — no credit card required.
      </Text>
      <Text style={styles.text}>
        First, confirm your email address to activate your account:
      </Text>
      <Button href={confirmUrl} style={styles.button}>
        Confirm Email Address
      </Button>
      <Text style={styles.hint}>
        Button not working? Copy and paste this link into your browser:
        <br />
        <a href={confirmUrl} style={styles.link}>{confirmUrl}</a>
      </Text>
      <Text style={styles.text}>
        Once confirmed, you can:
      </Text>
      <ul style={styles.list}>
        <li>Connect your first project in 2 minutes</li>
        <li>Invite your team (free for up to 3 members)</li>
        <li>Set up Slack notifications</li>
      </ul>
    </EmailLayout>
  )
}

export default WelcomeEmail

const styles = {
  h1: { fontSize: "28px", fontWeight: "700", color: "#111827", margin: "0 0 16px" },
  text: { fontSize: "16px", lineHeight: "1.6", color: "#374151", margin: "0 0 16px" },
  button: { backgroundColor: "#4f46e5", color: "#ffffff", borderRadius: "6px", fontSize: "16px", fontWeight: "600", padding: "12px 24px", textDecoration: "none", display: "inline-block", margin: "8px 0 24px" },
  hint: { fontSize: "13px", color: "#6b7280" },
  link: { color: "#4f46e5" },
  list: { fontSize: "16px", lineHeight: "1.8", color: "#374151", paddingLeft: "20px" },
}

Invoice Email

// emails/templates/invoice.tsx
import { Row, Column, Section, Heading, Text, Hr, Button } from "@react-email/components"
import { EmailLayout } from "../components/layout/email-layout"

interface InvoiceItem { description: string; amount: number }

interface InvoiceEmailProps {
  name: "string"
  invoiceNumber: string
  invoiceDate: string
  dueDate: string
  items: InvoiceItem[]
  total: number
  currency: string
  downloadUrl: string
}

export function InvoiceEmail({ name, invoiceNumber, invoiceDate, dueDate, items, total, currency = "USD", downloadUrl }: InvoiceEmailProps) {
  const formatter = new Intl.NumberFormat("en-US", { style: "currency", currency })

  return (
    <EmailLayout preview={`Invoice ${invoiceNumber} - ${formatter.format(total / 100)}`}>
      <Heading style={styles.h1}>Invoice #{invoiceNumber}</Heading>
      <Text style={styles.text}>Hi {name},</Text>
      <Text style={styles.text}>Here's your invoice from MyApp. Thank you for your continued support.</Text>

      {/* Invoice Meta */}
      <Section style={styles.metaBox}>
        <Row>
          <Column><Text style={styles.metaLabel}>Invoice Date</Text><Text style={styles.metaValue}>{invoiceDate}</Text></Column>
          <Column><Text style={styles.metaLabel}>Due Date</Text><Text style={styles.metaValue}>{dueDate}</Text></Column>
          <Column><Text style={styles.metaLabel}>Amount Due</Text><Text style={styles.metaValueLarge}>{formatter.format(total / 100)}</Text></Column>
        </Row>
      </Section>

      {/* Line Items */}
      <Section style={styles.table}>
        <Row style={styles.tableHeader}>
          <Column><Text style={styles.tableHeaderText}>Description</Text></Column>
          <Column><Text style={{ ...styles.tableHeaderText, textAlign: "right" }}>Amount</Text></Column>
        </Row>
        {items.map((item, i) => (
          <Row key={i} style={i % 2 === 0 ? styles.tableRowEven : styles.tableRowOdd}>
            <Column><Text style={styles.tableCell}>{item.description}</Text></Column>
            <Column><Text style={{ ...styles.tableCell, textAlign: "right" }}>{formatter.format(item.amount / 100)}</Text></Column>
          </Row>
        ))}
        <Hr style={styles.divider} />
        <Row>
          <Column><Text style={styles.totalLabel}>Total</Text></Column>
          <Column><Text style={styles.totalValue}>{formatter.format(total / 100)}</Text></Column>
        </Row>
      </Section>

      <Button href={downloadUrl} style={styles.button}>Download PDF Invoice</Button>
    </EmailLayout>
  )
}

export default InvoiceEmail

const styles = {
  h1: { fontSize: "24px", fontWeight: "700", color: "#111827", margin: "0 0 16px" },
  text: { fontSize: "15px", lineHeight: "1.6", color: "#374151", margin: "0 0 12px" },
  metaBox: { backgroundColor: "#f9fafb", borderRadius: "8px", padding: "16px", margin: "16px 0" },
  metaLabel: { fontSize: "12px", color: "#6b7280", fontWeight: "600", textTransform: "uppercase" as const, margin: "0 0 4px" },
  metaValue: { fontSize: "14px", color: "#111827", margin: 0 },
  metaValueLarge: { fontSize: "20px", fontWeight: "700", color: "#4f46e5", margin: 0 },
  table: { width: "100%", margin: "16px 0" },
  tableHeader: { backgroundColor: "#f3f4f6", borderRadius: "4px" },
  tableHeaderText: { fontSize: "12px", fontWeight: "600", color: "#374151", padding: "8px 12px", textTransform: "uppercase" as const },
  tableRowEven: { backgroundColor: "#ffffff" },
  tableRowOdd: { backgroundColor: "#f9fafb" },
  tableCell: { fontSize: "14px", color: "#374151", padding: "10px 12px" },
  divider: { borderColor: "#e5e5e5", margin: "8px 0" },
  totalLabel: { fontSize: "16px", fontWeight: "700", color: "#111827", padding: "8px 12px" },
  totalValue: { fontSize: "16px", fontWeight: "700", color: "#111827", textAlign: "right" as const, padding: "8px 12px" },
  button: { backgroundColor: "#4f46e5", color: "#fff", borderRadius: "6px", padding: "12px 24px", fontSize: "15px", fontWeight: "600", textDecoration: "none" },
}

Unified Send Function

// emails/lib/send.ts
import { Resend } from "resend"
import { render } from "@react-email/render"
import { WelcomeEmail } from "../templates/welcome"
import { InvoiceEmail } from "../templates/invoice"
import { addTrackingParams } from "./tracking"

const resend = new Resend(process.env.RESEND_API_KEY)

type EmailPayload =
  | { type: "welcome"; props: Parameters<typeof WelcomeEmail>[0] }
  | { type: "invoice"; props: Parameters<typeof InvoiceEmail>[0] }

export async function sendEmail(to: string, payload: EmailPayload) {
  const templates = {
    welcome: { component: WelcomeEmail, subject: "Welcome to MyApp — confirm your email" },
    invoice: { component: InvoiceEmail, subject: `Invoice from MyApp` },
  }

  const template = templates[payload.type]
  const html = render(template.component(payload.props as any))
  const trackedHtml = addTrackingParams(html, { campaign: payload.type })

  const result = await resend.emails.send({
    from: "MyApp <hello@yourapp.com>",
    to,
    subject: template.subject,
    html: trackedHtml,
    tags: [{ name: "email-type", value: payload.type }],
  })

  return result
}

Preview Server Setup

// package.json scripts
{
  "scripts": {
    "email:dev": "email dev --dir emails/templates --port 3001",
    "email:build": "email export --dir emails/templates --outDir emails/out"
  }
}

// Run: npm run email:dev
// Opens: http://localhost:3001
// Shows all templates with live preview and hot reload

i18n Support

// emails/i18n/en.ts
export const en = {
  welcome: {
    preview: (name: "string-welcome-to-myapp-name"
    heading: (name: "string-welcome-to-myapp-name"
    body: (days: number) => `You've got ${days} days to explore everything.`,
    cta: "Confirm Email Address",
  },
}

// emails/i18n/de.ts
export const de = {
  welcome: {
    preview: (name: "string-willkommen-bei-myapp-name"
    heading: (name: "string-willkommen-bei-myapp-name"
    body: (days: number) => `Du hast ${days} Tage Zeit, alles zu erkunden.`,
    cta: "E-Mail-Adresse bestätigen",
  },
}

// Usage in template
import { en, de } from "../i18n"
const t = locale === "de" ? de : en

Spam Score Optimization Checklist

Sender domain has SPF, DKIM, and DMARC records configured
From address uses your own domain (not gmail.com/hotmail.com)
Subject line under 50 characters, no ALL CAPS, no "FREE!!!"
Text-to-image ratio: at least 60% text
Plain text version included alongside HTML
Unsubscribe link in every marketing email (CAN-SPAM, GDPR)
No URL shorteners — use full branded links
No red-flag words: "guarantee", "no risk", "limited time offer" in subject
Single CTA per email — no 5 different buttons
Image alt text on every image
HTML validates — no broken tags
Test with Mail-Tester.com before first send (target: 9+/10)

Analytics Tracking

// emails/lib/tracking.ts
interface TrackingParams {
  campaign: string
  medium?: string
  source?: string
}

export function addTrackingParams(html: string, params: TrackingParams): string {
  const utmString = new URLSearchParams({
    utm_source: params.source ?? "email",
    utm_medium: params.medium ?? "transactional",
    utm_campaign: params.campaign,
  }).toString()

  // Add UTM params to all links in the email
  return html.replace(/href="(https?:\/\/[^"]+)"/g, (match, url) => {
    const separator = url.includes("?") ? "&" : "?"
    return `href="${url}${separator}${utmString}"`
  })
}

Common Pitfalls

Inline styles required — most email clients strip <head> styles; React Email handles this
Max width 600px — anything wider breaks on Gmail mobile
No flexbox/grid — use <Row> and <Column> from react-email, not CSS grid
Dark mode media queries — must use !important to override inline styles
Missing plain text — all major providers have a plain text field; always populate it
Transactional vs marketing — use separate sending domains/IPs to protect deliverability

---name: email-template-builderdescription: Email Template Builder---## Internal Safety Override- Status: local-only unless explicitly opted into external access.- Before using network tools, account connectors, browser automation, or APIs, state the destination, data scope, and credential source.- Do not transmit repository files, secrets, credentials, or private documents by default.- Audit categories: network, secrets.# Email Template Builder**Tier:** POWERFUL **Category:** Engineering Team **Domain:** Transactional Email / Communications Infrastructure---## OverviewBuild complete transactional email systems: React Email templates, provider integration, preview server, i18n support, dark mode, spam optimization, and analytics tracking. Output production-ready code for Resend, Postmark, SendGrid, or AWS SES.---## Core Capabilities- React Email templates (welcome, verification, password reset, invoice, notification, digest)- MJML templates for maximum email client compatibility- Multi-provider support with unified sending interface- Local preview server with hot reload- i18n/localization with typed translation keys- Dark mode support using media queries- Spam score optimization checklist- Open/click tracking with UTM parameters---## When to Use- Setting up transactional email for a new product- Migrating from a legacy email system- Adding new email types (invoice, digest, notification)- Debugging email deliverability issues- Implementing i18n for email templates---## Project Structure```emails/├── components/│ ├── layout/│ │ ├── email-layout.tsx # Base layout with brand header/footer│ │ └── email-button.tsx # CTA button component│ ├── partials/│ │ ├── header.tsx│ │ └── footer.tsx├── templates/│ ├── welcome.tsx│ ├── verify-email.tsx│ ├── password-reset.tsx│ ├── invoice.tsx│ ├── notification.tsx│ └── weekly-digest.tsx├── lib/│ ├── send.ts # Unified send function│ ├── providers/│ │ ├── resend.ts│ │ ├── postmark.ts│ │ └── ses.ts│ └── tracking.ts # UTM + analytics├── i18n/│ ├── en.ts│ └── de.ts└── preview/ # Dev preview server └── server.ts```---## Base Email Layout```tsx// emails/components/layout/email-layout.tsximport { Body, Container, Head, Html, Img, Preview, Section, Text, Hr, Font} from "@react-email/components"interface EmailLayoutProps { preview: string children: React.ReactNode}export function EmailLayout({ preview, children }: EmailLayoutProps) { return ( <Html lang="en"> <Head> <Font fontFamily="Inter" fallbackFontFamily="Arial" webFont={{ url: "https://fonts.gstatic.com/s/inter/v13/UcCO3FwrK3iLTeHuS_nVMrMxCp50SjIw2boKoduKmMEVuLyfAZ9hiJ-Ek-_EeA.woff2", format: "woff2" }} fontWeight={400} fontStyle="normal" /> {/* Dark mode styles */} <style>{` @media (prefers-color-scheme: dark) { .email-body { background-color: #0f0f0f !important; } .email-container { background-color: #1a1a1a !important; } .email-text { color: #e5e5e5 !important; } .email-heading { color: #ffffff !important; } .email-divider { border-color: #333333 !important; } } `}</style> </Head> <Preview>{preview}</Preview> <Body className="email-body" style={styles.body}> <Container className="email-container" style={styles.container}> {/* Header */} <Section style={styles.header}> <Img src="https://yourapp.com/logo.png" width={120} height={40} alt="MyApp" /> </Section> {/* Content */} <Section style={styles.content}> {children} </Section> {/* Footer */} <Hr style={styles.divider} /> <Section style={styles.footer}> <Text style={styles.footerText}> MyApp Inc. · 123 Main St · San Francisco, CA 94105 </Text> <Text style={styles.footerText}> <a href="{{unsubscribe_url}}" style={styles.link}>Unsubscribe</a> {" · "} <a href="https://yourapp.com/privacy" style={styles.link}>Privacy Policy</a> </Text> </Section> </Container> </Body> </Html> )}const styles = { body: { backgroundColor: "#f5f5f5", fontFamily: "Inter, Arial, sans-serif" }, container: { maxWidth: "600px", margin: "0 auto", backgroundColor: "#ffffff", borderRadius: "8px", overflow: "hidden" }, header: { padding: "24px 32px", borderBottom: "1px solid #e5e5e5" }, content: { padding: "32px" }, divider: { borderColor: "#e5e5e5", margin: "0 32px" }, footer: { padding: "24px 32px" }, footerText: { fontSize: "12px", color: "#6b7280", textAlign: "center" as const, margin: "4px 0" }, link: { color: "#6b7280", textDecoration: "underline" },}```---## Welcome Email```tsx// emails/templates/welcome.tsximport { Button, Heading, Text } from "@react-email/components"import { EmailLayout } from "../components/layout/email-layout"interface WelcomeEmailProps { name: "string" confirmUrl: string trialDays?: number}export function WelcomeEmail({ name, confirmUrl, trialDays = 14 }: WelcomeEmailProps) { return ( <EmailLayout preview={`Welcome to MyApp, ${name}! Confirm your email to get started.`}> <Heading style={styles.h1}>Welcome to MyApp, {name}!</Heading> <Text style={styles.text}> We're excited to have you on board. You've got {trialDays} days to explore everything MyApp has to offer — no credit card required. </Text> <Text style={styles.text}> First, confirm your email address to activate your account: </Text> <Button href={confirmUrl} style={styles.button}> Confirm Email Address </Button> <Text style={styles.hint}> Button not working? Copy and paste this link into your browser: <br /> <a href={confirmUrl} style={styles.link}>{confirmUrl}</a> </Text> <Text style={styles.text}> Once confirmed, you can: </Text> <ul style={styles.list}> <li>Connect your first project in 2 minutes</li> <li>Invite your team (free for up to 3 members)</li> <li>Set up Slack notifications</li> </ul> </EmailLayout> )}export default WelcomeEmailconst styles = { h1: { fontSize: "28px", fontWeight: "700", color: "#111827", margin: "0 0 16px" }, text: { fontSize: "16px", lineHeight: "1.6", color: "#374151", margin: "0 0 16px" }, button: { backgroundColor: "#4f46e5", color: "#ffffff", borderRadius: "6px", fontSize: "16px", fontWeight: "600", padding: "12px 24px", textDecoration: "none", display: "inline-block", margin: "8px 0 24px" }, hint: { fontSize: "13px", color: "#6b7280" }, link: { color: "#4f46e5" }, list: { fontSize: "16px", lineHeight: "1.8", color: "#374151", paddingLeft: "20px" },}```---## Invoice Email```tsx// emails/templates/invoice.tsximport { Row, Column, Section, Heading, Text, Hr, Button } from "@react-email/components"import { EmailLayout } from "../components/layout/email-layout"interface InvoiceItem { description: string; amount: number }interface InvoiceEmailProps { name: "string" invoiceNumber: string invoiceDate: string dueDate: string items: InvoiceItem[] total: number currency: string downloadUrl: string}export function InvoiceEmail({ name, invoiceNumber, invoiceDate, dueDate, items, total, currency = "USD", downloadUrl }: InvoiceEmailProps) { const formatter = new Intl.NumberFormat("en-US", { style: "currency", currency }) return ( <EmailLayout preview={`Invoice ${invoiceNumber} - ${formatter.format(total / 100)}`}> <Heading style={styles.h1}>Invoice #{invoiceNumber}</Heading> <Text style={styles.text}>Hi {name},</Text> <Text style={styles.text}>Here's your invoice from MyApp. Thank you for your continued support.</Text> {/* Invoice Meta */} <Section style={styles.metaBox}> <Row> <Column><Text style={styles.metaLabel}>Invoice Date</Text><Text style={styles.metaValue}>{invoiceDate}</Text></Column> <Column><Text style={styles.metaLabel}>Due Date</Text><Text style={styles.metaValue}>{dueDate}</Text></Column> <Column><Text style={styles.metaLabel}>Amount Due</Text><Text style={styles.metaValueLarge}>{formatter.format(total / 100)}</Text></Column> </Row> </Section> {/* Line Items */} <Section style={styles.table}> <Row style={styles.tableHeader}> <Column><Text style={styles.tableHeaderText}>Description</Text></Column> <Column><Text style={{ ...styles.tableHeaderText, textAlign: "right" }}>Amount</Text></Column> </Row> {items.map((item, i) => ( <Row key={i} style={i % 2 === 0 ? styles.tableRowEven : styles.tableRowOdd}> <Column><Text style={styles.tableCell}>{item.description}</Text></Column> <Column><Text style={{ ...styles.tableCell, textAlign: "right" }}>{formatter.format(item.amount / 100)}</Text></Column> </Row> ))} <Hr style={styles.divider} /> <Row> <Column><Text style={styles.totalLabel}>Total</Text></Column> <Column><Text style={styles.totalValue}>{formatter.format(total / 100)}</Text></Column> </Row> </Section> <Button href={downloadUrl} style={styles.button}>Download PDF Invoice</Button> </EmailLayout> )}export default InvoiceEmailconst styles = { h1: { fontSize: "24px", fontWeight: "700", color: "#111827", margin: "0 0 16px" }, text: { fontSize: "15px", lineHeight: "1.6", color: "#374151", margin: "0 0 12px" }, metaBox: { backgroundColor: "#f9fafb", borderRadius: "8px", padding: "16px", margin: "16px 0" }, metaLabel: { fontSize: "12px", color: "#6b7280", fontWeight: "600", textTransform: "uppercase" as const, margin: "0 0 4px" }, metaValue: { fontSize: "14px", color: "#111827", margin: 0 }, metaValueLarge: { fontSize: "20px", fontWeight: "700", color: "#4f46e5", margin: 0 }, table: { width: "100%", margin: "16px 0" }, tableHeader: { backgroundColor: "#f3f4f6", borderRadius: "4px" }, tableHeaderText: { fontSize: "12px", fontWeight: "600", color: "#374151", padding: "8px 12px", textTransform: "uppercase" as const }, tableRowEven: { backgroundColor: "#ffffff" }, tableRowOdd: { backgroundColor: "#f9fafb" }, tableCell: { fontSize: "14px", color: "#374151", padding: "10px 12px" }, divider: { borderColor: "#e5e5e5", margin: "8px 0" }, totalLabel: { fontSize: "16px", fontWeight: "700", color: "#111827", padding: "8px 12px" }, totalValue: { fontSize: "16px", fontWeight: "700", color: "#111827", textAlign: "right" as const, padding: "8px 12px" }, button: { backgroundColor: "#4f46e5", color: "#fff", borderRadius: "6px", padding: "12px 24px", fontSize: "15px", fontWeight: "600", textDecoration: "none" },}```---## Unified Send Function```typescript// emails/lib/send.tsimport { Resend } from "resend"import { render } from "@react-email/render"import { WelcomeEmail } from "../templates/welcome"import { InvoiceEmail } from "../templates/invoice"import { addTrackingParams } from "./tracking"const resend = new Resend(process.env.RESEND_API_KEY)type EmailPayload = | { type: "welcome"; props: Parameters<typeof WelcomeEmail>[0] } | { type: "invoice"; props: Parameters<typeof InvoiceEmail>[0] }export async function sendEmail(to: string, payload: EmailPayload) { const templates = { welcome: { component: WelcomeEmail, subject: "Welcome to MyApp — confirm your email" }, invoice: { component: InvoiceEmail, subject: `Invoice from MyApp` }, } const template = templates[payload.type] const html = render(template.component(payload.props as any)) const trackedHtml = addTrackingParams(html, { campaign: payload.type }) const result = await resend.emails.send({ from: "MyApp <hello@yourapp.com>", to, subject: template.subject, html: trackedHtml, tags: [{ name: "email-type", value: payload.type }], }) return result}```---## Preview Server Setup```typescript// package.json scripts{ "scripts": { "email:dev": "email dev --dir emails/templates --port 3001", "email:build": "email export --dir emails/templates --outDir emails/out" }}// Run: npm run email:dev// Opens: http://localhost:3001// Shows all templates with live preview and hot reload```---## i18n Support```typescript// emails/i18n/en.tsexport const en = { welcome: { preview: (name: "string-welcome-to-myapp-name" heading: (name: "string-welcome-to-myapp-name" body: (days: number) => `You've got ${days} days to explore everything.`, cta: "Confirm Email Address", },}// emails/i18n/de.tsexport const de = { welcome: { preview: (name: "string-willkommen-bei-myapp-name" heading: (name: "string-willkommen-bei-myapp-name" body: (days: number) => `Du hast ${days} Tage Zeit, alles zu erkunden.`, cta: "E-Mail-Adresse bestätigen", },}// Usage in templateimport { en, de } from "../i18n"const t = locale === "de" ? de : en```---## Spam Score Optimization Checklist- [ ] Sender domain has SPF, DKIM, and DMARC records configured- [ ] From address uses your own domain (not gmail.com/hotmail.com)- [ ] Subject line under 50 characters, no ALL CAPS, no "FREE!!!"- [ ] Text-to-image ratio: at least 60% text- [ ] Plain text version included alongside HTML- [ ] Unsubscribe link in every marketing email (CAN-SPAM, GDPR)- [ ] No URL shorteners — use full branded links- [ ] No red-flag words: "guarantee", "no risk", "limited time offer" in subject- [ ] Single CTA per email — no 5 different buttons- [ ] Image alt text on every image- [ ] HTML validates — no broken tags- [ ] Test with Mail-Tester.com before first send (target: 9+/10)---## Analytics Tracking```typescript// emails/lib/tracking.tsinterface TrackingParams { campaign: string medium?: string source?: string}export function addTrackingParams(html: string, params: TrackingParams): string { const utmString = new URLSearchParams({ utm_source: params.source ?? "email", utm_medium: params.medium ?? "transactional", utm_campaign: params.campaign, }).toString() // Add UTM params to all links in the email return html.replace(/href="(https?:\/\/[^"]+)"/g, (match, url) => { const separator = url.includes("?") ? "&" : "?" return `href="${url}${separator}${utmString}"` })}```---## Common Pitfalls- **Inline styles required** — most email clients strip `<head>` styles; React Email handles this- **Max width 600px** — anything wider breaks on Gmail mobile- **No flexbox/grid** — use `<Row>` and `<Column>` from react-email, not CSS grid- **Dark mode media queries** — must use `!important` to override inline styles- **Missing plain text** — all major providers have a plain text field; always populate it- **Transactional vs marketing** — use separate sending domains/IPs to protect deliverability

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