Antigravity Agent
165 lines
4.9 KiB
Markdown
165 lines
4.9 KiB
Markdown
---
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id: backend-transactional-email
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title: Transactional Email — Resend / SendGrid / 템플릿
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category: Coding
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status: draft
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source_trust_level: B
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verification_status: conceptual
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created_at: 2026-05-09
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updated_at: 2026-05-09
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tags: [backend, email, transactional, vibe-coding]
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tech_stack: { language: "TS / React Email", applicable_to: ["Backend"] }
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applied_in: []
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aliases: [transactional email, Resend, SendGrid, Postmark, React Email, MJML, SPF DKIM]
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---
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# Transactional Email
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> 사용자 행동 트리거 (가입, 영수증). **마케팅과 분리, 별 IP / 별 도메인 권장**. 도구: Resend / Postmark / SendGrid. 템플릿: React Email / MJML. SPF/DKIM/DMARC 필수.
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## 📖 핵심 개념
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- Transactional vs Marketing: 다른 IP / 도메인 / sender reputation.
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- SPF / DKIM / DMARC: spoofing 방어 + spam 회피.
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- Bounce / Complaint: 처리 안 하면 reputation 망가짐.
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- Idempotency: 같은 이벤트로 두 번 보내면 안 됨.
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## 💻 코드 패턴
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### Resend (modern)
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```ts
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import { Resend } from 'resend';
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const resend = new Resend(process.env.RESEND_API_KEY);
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await resend.emails.send({
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from: 'Acme <noreply@mail.acme.com>',
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to: user.email,
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subject: 'Welcome to Acme',
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html: render(<WelcomeEmail name={user.name} />),
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headers: { 'X-Idempotency-Key': eventId },
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});
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```
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### React Email 템플릿
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```tsx
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import { Body, Container, Head, Heading, Html, Link, Preview, Text } from '@react-email/components';
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export function WelcomeEmail({ name }: { name: string }) {
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return (
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<Html>
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<Head />
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<Preview>Welcome to Acme, {name}</Preview>
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<Body style={{ backgroundColor: '#f6f9fc', fontFamily: 'system-ui' }}>
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<Container style={{ padding: '40px 20px' }}>
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<Heading>Welcome, {name}!</Heading>
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<Text>Click <Link href="https://acme.com/start">here</Link> to start.</Text>
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</Container>
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</Body>
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</Html>
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);
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}
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```
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```ts
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import { render } from '@react-email/render';
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const html = await render(<WelcomeEmail name="A" />);
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const text = await render(<WelcomeEmail name="A" />, { plainText: true });
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```
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### 큐 + retry
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```ts
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// 직접 보내지 말고 큐
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queue.add('email', { to, template, data, idempotencyKey });
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queue.process('email', async (job) => {
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const sent = await db.emails.find(job.data.idempotencyKey);
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if (sent) return; // 이미 보냄
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const r = await resend.emails.send({...});
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await db.emails.insert({ idempotencyKey: job.data.idempotencyKey, providerId: r.id });
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});
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```
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### Bounce / complaint webhook
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```ts
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app.post('/webhooks/email', async (req, res) => {
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// SES SNS / SendGrid event webhook / Resend webhook
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const ev = req.body;
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if (ev.type === 'email.bounced') {
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await db.users.update(ev.email, { emailValid: false });
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}
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if (ev.type === 'email.complained') {
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await db.users.update(ev.email, { emailMarketingOptOut: true, emailValid: false });
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}
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res.json({ ok: true });
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});
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```
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### SPF / DKIM / DMARC DNS
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```
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# SPF
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mail.acme.com. TXT "v=spf1 include:_spf.resend.com -all"
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# DKIM (Resend / SendGrid 가 제공하는 CNAME)
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resend._domainkey.mail.acme.com. CNAME resend._domainkey.acme.com.resend.email.
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# DMARC
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_dmarc.mail.acme.com. TXT "v=DMARC1; p=quarantine; rua=mailto:dmarc@acme.com"
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```
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### Marketing 분리
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```
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Transactional: noreply@mail.acme.com
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Marketing: hello@news.acme.com
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```
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다른 sub-domain → bounce 가 transactional 평판에 안 영향.
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### Plain text + HTML 둘 다
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```ts
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await resend.emails.send({
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from, to, subject,
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html: render(<Email />),
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text: render(<Email />, { plainText: true }), // spam 점수 낮춤
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});
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```
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### Preview tools
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- React Email dev server: 라이브 preview.
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- Mailtrap / Litmus: 다양한 client 렌더 테스트.
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### 다국어
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```ts
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const html = await render(<WelcomeEmail name={name} t={i18n.t} />, { locale: user.locale });
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```
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## 🤔 의사결정 기준
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| 종류 | 추천 |
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|---|---|
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| 작은 SaaS / modern stack | Resend |
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| 큰 규모 / 분석 강함 | SendGrid / Mailgun |
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| Bounce 까다로움 | Postmark (transactional 전문) |
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| 자체 메일 서버 | SES (싸지만 복잡) |
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| Email 아닌 SMS | Twilio / MessageBird |
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| 마케팅 자동화 | Customer.io / Loops |
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## ❌ 안티패턴
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- **DKIM 없음**: spam 폴더 직행.
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- **Marketing 같은 도메인**: bounce 가 transactional 평판 망가짐.
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- **Bounce 처리 안 함**: 평판 추락 → 모두 spam.
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- **Throttle 없이 대량**: rate limit hit.
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- **Idempotency 없음**: 같은 이벤트 여러 번 메일.
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- **Plain text 누락**: 일부 client / spam 점수 ↑.
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- **Inline image base64**: 큰 메일 + 일부 client 차단. 호스팅된 URL.
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- **Subject 가 spam-trigger**: "FREE!!!" 같은.
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## 🤖 LLM 활용 힌트
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- Resend + React Email + 큐 + bounce webhook 4종.
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- SPF/DKIM/DMARC 자동 사이트 (mxtoolbox) 검증.
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- transactional 따로 sub-domain.
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## 🔗 관련 문서
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- [[Backend_Webhook_Patterns]]
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- [[Backend_Job_Queue_Patterns]]
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- [[Frontend_i18n_Patterns]]
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