Email Deliverability Best Practices dengan Resend di Helipod

Email terkirim ≠ Email sampai ke inbox

Email terkirim → Processing → Filtering → Inbox/Spam
                    ↑              ↑
              Authentication   Reputation

DNS Record:
Type: TXT
Name: @
Value: v=spf1 include:sendgrid.net ~all

DNS Record:
Type: TXT
Name: resend._domainkey
Value: v=DKIM1; k=rsa; p=MIGfMA0GCSqGSIb3DQEBAQUAA...

DNS Record:
Type: TXT
Name: _dmarc
Value: v=DMARC1; p=quarantine; rua=mailto:dmarc@helipod.io

Domain baru → Langsung kirim 1000 email → Spam!
Domain baru → Gradually increase → Inbox

Minggu 1: 10-20 email/hari
Minggu 2: 30-50 email/hari
Minggu 3: 100-200 email/hari
Minggu 4: 300-500 email/hari
Minggu 5: 500-1000 email/hari

// Warm up scheduler
const WARM_UP_SCHEDULE = [
  { week: 1, dailyLimit: 20 },
  { week: 2, dailyLimit: 50 },
  { week: 3, dailyLimit: 200 },
  { week: 4, dailyLimit: 500 },
  { week: 5, dailyLimit: 1000 },
];

async function sendWithWarmUp(email) {
  const domainAge = getDomainAge(email.from);
  const schedule = WARM_UP_SCHEDULE.find(s => 
    domainAge >= (s.week - 1) * 7 && domainAge < s.week * 7
  );
  
  const sentToday = await getSentCountToday(email.from);
  if (sentToday >= schedule.dailyLimit) {
    throw new Error('Daily limit reached');
  }
  
  return await resend.emails.send(email);
}

# ❌ Hindari
"FREE!!! Click here now!!!"
"URGENT: Your account will be closed"
"Buy now, limited time offer"

# ✅ Gunakan
"Your invoice from Helipod"
"Welcome to Helipod"
"Password reset request"

<!-- ❌ Hindari -->
<html>
<body>
  <h1 style="color: red; font-size: 24px;">BELI SEKARANG!!!</h1>
  <p>Klik di sini untuk mendapatkan DISKON 90%!!!</p>
  <a href="http://bit.ly/xxx">KLIK DI SINI</a>
</body>
</html>

<!-- ✅ Gunakan -->
<html>
<body style="font-family: Arial, sans-serif; color: #333;">
  <h1>Selamat datang di Helipod!</h1>
  <p>Halo Budi,</p>
  <p>Akun kamu sudah aktif. Mulai deploy aplikasi sekarang.</p>
  <a href="https://helipod.io/dashboard" 
     style="background: #10b981; color: white; padding: 10px 20px; text-decoration: none;">
    Dashboard
  </a>
</body>
</html>

// Hapus email bounce
async function cleanBouncedEmails() {
  const emails = await resend.emails.list();
  
  for (const email of emails) {
    if (email.last_event === 'bounced') {
      await removeFromList(email.to);
      console.log(`Removed bounced: ${email.to}`);
    }
  }
}

// Validasi sebelum kirim
function validateEmail(email) {
  // Cek format
  const emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
  if (!emailRegex.test(email)) return false;
  
  // Cek disposable email
  const disposableDomains = ['tempmail.com', 'throwaway.email'];
  const domain = email.split('@')[1];
  if (disposableDomains.includes(domain)) return false;
  
  return true;
}

// Double opt-in untuk newsletter
async function subscribe(email) {
  // 1. Kirim email konfirmasi
  await resend.emails.send({
    from: 'noreply@helipod.io',
    to: email,
    subject: 'Konfirmasi subscription',
    html: `
      <p>Klik link untuk konfirmasi:</p>
      <a href="https://helipod.io/confirm?token=${token}">
        Konfirmasi
      </a>
    `
  });
  
  // 2. Tunggu konfirmasi
  // 3. Tambahkan ke list setelah konfirmasi
}

1. Delivery Rate
   - Target: > 95%
   - Alert: < 90%

2. Bounce Rate
   - Target: < 2%
   - Alert: > 5%

3. Open Rate
   - Target: > 20%
   - Alert: < 10%

4. Spam Complaint Rate
   - Target: < 0.1%
   - Alert: > 0.3%

Email Analytics:
├── Total sent: 12,345
├── Delivered: 12,100 (98%)
├── Opened: 4,500 (37%)
├── Clicked: 1,200 (10%)
├── Bounced: 145 (1.2%)
└── Complaints: 5 (0.04%)

// Alert jika bounce rate tinggi
async function checkDeliverability() {
  const stats = await resend.analytics.get();
  
  const bounceRate = stats.bounced / stats.sent;
  const complaintRate = stats.complaints / stats.sent;
  
  if (bounceRate > 0.05) {
    await sendAlert(`High bounce rate: ${(bounceRate * 100).toFixed(1)}%`);
  }
  
  if (complaintRate > 0.003) {
    await sendAlert(`High complaint rate: ${(complaintRate * 100).toFixed(2)}%`);
  }
}

// Jangan kirim ke email yang bounce
async function shouldSend(email) {
  const history = await getSendHistory(email);
  
  // Hard bounce = jangan kirim lagi
  if (history.hardBounces > 0) {
    return false;
  }
  
  // Soft bounce = coba lagi nanti
  if (history.softBounces > 3) {
    return false;
  }
  
  return true;
}

// Jika user complain, jangan kirim lagi
async function handleComplaint(email) {
  await removeFromAllLists(email);
  await addToSuppressionList(email);
  
  console.log(`Complaint from ${email} - suppressed`);
}

// Kirim berdasarkan segment
const segments = {
  active: users.filter(u => u.lastLogin > daysAgo(30)),
  inactive: users.filter(u => u.lastLogin <= daysAgo(30)),
  trial: users.filter(u => u.plan === 'trial'),
};

// Personalisasi berdasarkan behavior
async function sendPersonalizedEmail(user) {
  const recommendations = await getRecommendations(user.id);
  
  await resend.emails.send({
    to: user.email,
    subject: `Rekomendasi untuk ${user.name}`,
    html: `
      <h1>Halo ${user.name}!</h1>
      <p>Berdasarkan aktivitas kamu, kami rekomendasikan:</p>
      <ul>
        ${recommendations.map(r => `<li>${r.name}</li>`).join('')}
      </ul>
    `
  });
}

// A/B testing subject line
async function abTest(users) {
  const half = Math.floor(users.length / 2);
  
  // Group A
  await sendBatch(users.slice(0, half), {
    subject: 'Selamat datang di Helipod!'
  });
  
  // Group B
  await sendBatch(users.slice(half), {
    subject: 'Akun kamu sudah aktif!'
  });
  
  // Compare open rates
}