email-systems
Email has the highest ROI of any marketing channel. $36 for every $1 spent. Yet most startups treat it as an afterthought - bulk blasts, no personalization, landing in spam folders.
What this skill does
# Email Systems
Email has the highest ROI of any marketing channel. $36 for every $1 spent.
Yet most startups treat it as an afterthought - bulk blasts, no personalization,
landing in spam folders.
This skill covers transactional email that works, marketing automation that
converts, deliverability that reaches inboxes, and the infrastructure decisions
that scale.
## Principles
- Transactional vs Marketing separation | Description: Transactional emails (password reset, receipts) need 100% delivery.
Marketing emails (newsletters, promos) have lower priority. Use separate
IP addresses and providers to protect transactional deliverability. | Examples: Good: Password resets via Postmark, marketing via ConvertKit | Bad: All emails through one SendGrid account
- Permission is everything | Description: Only email people who asked to hear from you. Double opt-in for marketing.
Easy unsubscribe. Clean your list ruthlessly. Bad lists destroy deliverability. | Examples: Good: Confirmed subscription + one-click unsubscribe | Bad: Scraped email list, hidden unsubscribe, bought contacts
- Deliverability is infrastructure | Description: SPF, DKIM, DMARC are not optional. Warm up new IPs. Monitor bounce rates.
Deliverability is earned through technical setup and good behavior. | Examples: Good: All DNS records configured, dedicated IP warmed for 4 weeks | Bad: Using free tier shared IP, no authentication records
- One email, one goal | Description: Each email should have exactly one purpose and one CTA. Multiple asks
means nothing gets clicked. Clear single action. | Examples: Good: "Click here to verify your email" (one button) | Bad: "Verify email, check out our blog, follow us on Twitter, refer a friend..."
- Timing and frequency matter | Description: Wrong time = low open rates. Too frequent = unsubscribes. Let users
set preferences. Test send times. Respect inbox fatigue. | Examples: Good: Weekly digest on Tuesday 10am user's timezone, preference center | Bad: Daily emails at random times, no way to reduce frequency
## Patterns
### Transactional Email Queue
Queue all transactional emails with retry logic and monitoring
**When to use**: Sending any critical email (password reset, receipts, confirmations)
// Don't block request on email send
await queue.add('email', {
template: 'password-reset',
to: user.email,
data: { resetToken, expiresAt }
}, {
attempts: 3,
backoff: { type: 'exponential', delay: 2000 }
});
### Email Event Tracking
Track delivery, opens, clicks, bounces, and complaints
**When to use**: Any email campaign or transactional flow
# Track lifecycle:
- Queued: Email entered system
- Sent: Handed to provider
- Delivered: Reached inbox
- Opened: Recipient viewed
- Clicked: Recipient engaged
- Bounced: Permanent failure
- Complained: Marked as spam
### Template Versioning
Version email templates for rollback and A/B testing
**When to use**: Changing production email templates
templates/
password-reset/
v1.tsx (current)
v2.tsx (testing 10%)
v1-deprecated.tsx (archived)
# Deploy new version gradually
# Monitor metrics before full rollout
### Bounce Handling State Machine
Automatically handle bounces to protect sender reputation
**When to use**: Processing bounce and complaint webhooks
switch (bounceType) {
case 'hard':
await markEmailInvalid(email);
break;
case 'soft':
await incrementBounceCount(email);
if (count >= 3) await markEmailInvalid(email);
break;
case 'complaint':
await unsubscribeImmediately(email);
break;
}
### React Email Components
Build emails with reusable React components
**When to use**: Creating email templates
import { Button, Html } from '@react-email/components';
export default function WelcomeEmail({ userName }) {
return (
<Html>
<h1>Welcome {userName}!</h1>
<Button href="https://app.com/start">
Get Started
</Button>
</Html>
);
}
### Preference Center
Let users control email frequency and topics
**When to use**: Building marketing or notification systems
Preferences:
☑ Product updates (weekly)
☑ New features (monthly)
☐ Marketing promotions
☑ Account notifications (always)
# Respect preferences in all sends
# Required for GDPR compliance
## Sharp Edges
### Missing SPF, DKIM, or DMARC records
Severity: CRITICAL
Situation: Sending emails without authentication. Emails going to spam folder.
Low open rates. No idea why. Turns out DNS records were never set up.
Symptoms:
- Emails going to spam
- Low deliverability rates
- mail-tester.com score below 8
- No DMARC reports received
Why this breaks:
Email authentication (SPF, DKIM, DMARC) tells receiving servers you're
legit. Without them, you look like a spammer. Modern email providers
increasingly require all three.
Recommended fix:
# Required DNS records:
## SPF (Sender Policy Framework)
TXT record: v=spf1 include:_spf.google.com include:sendgrid.net ~all
## DKIM (DomainKeys Identified Mail)
TXT record provided by your email provider
Adds cryptographic signature to emails
## DMARC (Domain-based Message Authentication)
TXT record: v=DMARC1; p=quarantine; rua=mailto:[email protected]
# Verify setup:
- Send test email to mail-tester.com
- Check MXToolbox for record validation
- Monitor DMARC reports
### Using shared IP for transactional email
Severity: HIGH
Situation: Password resets going to spam. Using free tier of email provider.
Some other customer on your shared IP got flagged for spam.
Your reputation is ruined by association.
Symptoms:
- Transactional emails in spam
- Inconsistent delivery
- Using same provider for marketing and transactional
Why this breaks:
Shared IPs share reputation. One bad actor affects everyone. For
critical transactional email, you need your own IP or a provider
with strict shared IP policies.
Recommended fix:
# Transactional email strategy:
## Option 1: Dedicated IP (high volume)
- Get dedicated IP from your provider
- Warm it up slowly (start with 100/day)
- Maintain consistent volume
## Option 2: Transactional-only provider
- Postmark (very strict, great reputation)
- Includes shared pool with high standards
### Separate concerns:
- Transactional: Postmark or Resend
- Marketing: ConvertKit or Customer.io
- Never mix marketing and transactional
### Not processing bounce notifications
Severity: HIGH
Situation: Emailing same dead addresses over and over. Bounce rate climbing.
Email provider threatening to suspend account. List is 40% dead.
Symptoms:
- Bounce rate above 2%
- No webhook handlers for bounces
- Same emails failing repeatedly
Why this breaks:
Bounces damage sender reputation. Email providers track bounce rates.
Above 2% and you start looking like a spammer. Dead addresses must
be removed immediately.
Recommended fix:
# Bounce handling requirements:
### Hard bounces:
Remove immediately on first occurrence
Invalid address, domain doesn't exist
### Soft bounces:
Retry 3 times over 72 hours
After 3 failures, treat as hard bounce
### Implementation:
```typescript
// Webhook handler for bounces
app.post('/webhooks/email', (req, res) => {
const event = req.body;
if (event.type === 'bounce') {
await markEmailInvalid(event.email);
await removeFromAllLists(event.email);
}
});
```
### Monitor:
Track bounce rate by campaign
Alert if bounce rate exceeds 1%
### Missing or hidden unsubscribe link
Severity: CRITICAL
Situation: Users marking as spam because they cannot unsubscribe. Spam complaints
rising. CAN-SPAM violation. Email provider suspends account.
Symptoms:
- Hidden unsubscribe links
- Multi-step unsubscribe process
- No List-Unsubscribe header
- High spam complaint rate
Why this breaks:
Users who cannot unsubscribe will mark as spam. Spam complaints hurt
reputation more than unsubscribes. Also it is literally illegal.
CAN-SPAM, GDPR all require clear unsubscribe.
Recommended fix:
# Unsubscribe requirements:
### Visible:
- Above the fold in email footer
- Clear text, notRelated in Ads & Marketing
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