Email Template Builder
Build complete transactional email systems: React Email templates, provider integration (Resend, Postmark, SendGrid, AWS SES), preview server, i18n support, dark mode, spam optimization, analytics tracking. Use when adding transactional email to a new product, migrating between email providers, refactoring legacy email templates for accessibility, or adding internationalization to existing templates.
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SKILL.md
# 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
```tsx
// 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
```tsx
// 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
```tsx
// 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
```typescript
// 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 <[email protected]>",
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.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 ${days} Tage Zeit, alles zu erkunden.`,
cta: "E-Mail-Adresse bestätigen",
},
}
// Usage in template
import { en, de } from "../i18n"
const t = locale === "de" ? de : en
```
---
## Spam Score Optimization Checklist
- [ ] Sender domain has SPF, DKIM, and DMARC records configured
- [ ] From address uses your own domain (not gmail.com/hotmail.com)
- [ ] Subject line under 50 characters, no ALL CAPS, no "FREE!!!"
- [ ] Text-to-image ratio: at least 60% text
- [ ] Plain text version included alongside HTML
- [ ] Unsubscribe link in every marketing email (CAN-SPAM, GDPR)
- [ ] No URL shorteners — use full branded links
- [ ] No red-flag words: "guarantee", "no risk", "limited time offer" in subject
- [ ] Single CTA per email — no 5 different buttons
- [ ] Image alt text on every image
- [ ] HTML validates — no broken tags
- [ ] Test with Mail-Tester.com before first send (target: 9+/10)
---
## Analytics Tracking
```typescript
// emails/lib/tracking.ts
interface TrackingParams {
campaign: string
medium?: string
source?: string
}
export function addTrackingParams(html: string, params: TrackingParams): string {
const utmString = new URLSearchParams({
utm_source: params.source ?? "email",
utm_medium: params.medium ?? "transactional",
utm_campaign: params.campaign,
}).toString()
// Add UTM params to all links in the email
return html.replace(/href="(https?:\/\/[^"]+)"/g, (match, url) => {
const separator = url.includes("?") ? "&" : "?"
return `href="${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