// 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.
Behavioral guidelines to reduce common LLM coding mistakes. Use when writing, reviewing, or refactoring code to avoid overcomplication, make surgical changes, surface assumptions, and define verifiable success criteria.
Security audit, hardening, threat modeling (STRIDE/PASTA), Red/Blue Team, OWASP checks, code review, incident response, and infrastructure security for any project.
Important: Before you begin, fill in the generatedBy property in the meta section of .actor/actor.json. Replace it with the tool and model you're currently using, such as "Claude Code with Claude Sonnet 4.5". This helps Apify monitor and improve AGENTS.md for specific AI tools and models.
Fast, modern JavaScript/TypeScript development with the Bun runtime, inspired by [oven-sh/bun](https://github.com/oven-sh/bun).
Conduct comprehensive security assessments of cloud infrastructure across Microsoft Azure, Amazon Web Services (AWS), and Google Cloud Platform (GCP).
Guide developers through setting up development environments with proper tools, dependencies, and configurations
| name | email-systems |
| description | 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. |
| risk | none |
| source | vibeship-spawner-skills (Apache 2.0) |
| date_added | "2026-02-27T00:00:00.000Z" |
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.
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 } });
Track delivery, opens, clicks, bounces, and complaints
When to use: Any email campaign or transactional flow
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)
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; }
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 (
Let users control email frequency and topics
When to use: Building marketing or notification systems
Preferences: ā Product updates (weekly) ā New features (monthly) ā Marketing promotions ā Account notifications (always)
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:
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:
TXT record: v=spf1 include:_spf.google.com include:sendgrid.net ~all
TXT record provided by your email provider Adds cryptographic signature to emails
TXT record: v=DMARC1; p=quarantine; rua=mailto:dmarc@yourdomain.com
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:
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:
Severity: HIGH
Situation: Emailing same dead addresses over and over. Bounce rate climbing. Email provider threatening to suspend account. List is 40% dead.
Symptoms:
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:
Remove immediately on first occurrence Invalid address, domain doesn't exist
Retry 3 times over 72 hours After 3 failures, treat as hard bounce
// 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);
}
});
Track bounce rate by campaign Alert if bounce rate exceeds 1%
Severity: CRITICAL
Situation: Users marking as spam because they cannot unsubscribe. Spam complaints rising. CAN-SPAM violation. Email provider suspends account.
Symptoms:
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:
List-Unsubscribe: <mailto:unsubscribe@example.com>,
<https://example.com/unsubscribe?token=xxx>
List-Unsubscribe-Post: List-Unsubscribe=One-Click
Option to reduce frequency instead of full unsubscribe
Severity: MEDIUM
Situation: Some users see blank emails. Spam filters flagging emails. Accessibility issues for screen readers. Email clients that strip HTML show nothing.
Symptoms:
Why this breaks: Not everyone can render HTML. Screen readers work better with plain text. Spam filters are suspicious of HTML-only. Multipart is the standard.
Recommended fix:
await resend.emails.send({
from: 'you@example.com',
to: 'user@example.com',
subject: 'Welcome!',
html: '<h1>Welcome!</h1><p>Thanks for signing up.</p>',
text: 'Welcome!\n\nThanks for signing up.',
});
Use html-to-text library as fallback But hand-crafted plain text is better
Not just HTML stripped of tags Actual formatted text content
Severity: HIGH
Situation: Just switched providers. Started sending 50,000 emails/day immediately. Massive deliverability issues. New IP has no reputation. Looks like spam.
Symptoms:
Why this breaks: New IPs have no reputation. Sending high volume immediately looks like a spammer who just spun up. You need to gradually build trust.
Recommended fix:
Week 1: 50-100 emails/day Week 2: 200-500 emails/day Week 3: 500-1000 emails/day Week 4: 1000-5000 emails/day Continue doubling until at volume
Severity: CRITICAL
Situation: Bought an email list. Scraped emails from LinkedIn. Added conference contacts. Spam complaints through the roof. Provider suspends account. Maybe a lawsuit.
Symptoms:
Why this breaks: Permission-based email is not optional. It is the law (CAN-SPAM, GDPR). It is also effective - unwilling recipients hurt your metrics and reputation more than they help.
Recommended fix:
Password resets, receipts, account alerts do not need marketing opt-in
Severity: MEDIUM
Situation: Beautiful designed email that is one big image. Users with images blocked see nothing. Spam filters flag it. Mobile loading is slow. No one can copy text.
Symptoms:
Why this breaks: Images are blocked by default in many clients. Spam filters are suspicious of image-only emails. Accessibility suffers. Load times increase.
Recommended fix:
<img
src="hero.jpg"
alt="Save 50% this week - use code SAVE50"
style="max-width: 100%"
/>
<p>Use code <strong>SAVE50</strong> to save 50% this week.</p>
Severity: MEDIUM
Situation: Inbox shows "View this email in browser" or random HTML as preview. Lower open rates. First impression wasted on boilerplate.
Symptoms:
Why this breaks: Preview text is prime real estate - appears right after subject line. Default or missing preview text wastes this space. Good preview text increases open rates 10-30%.
Recommended fix:
<div style="display:none;max-height:0;overflow:hidden;">
Your preview text here. This appears in inbox preview.
<!-- Add whitespace to push footer text out -->
‌ ‌ ‌ ‌
</div>
<Preview>
Your preview text here. This appears in inbox preview.
</Preview>
Severity: HIGH
Situation: Sending to 10,000 users. API fails at 3,000. No tracking of what sent. Either double-send or lose 7,000. No way to know who got the email.
Symptoms:
Why this breaks: Bulk sends fail partially. APIs timeout. Rate limits hit. Without tracking individual send status, you cannot recover gracefully.
Recommended fix:
async function sendCampaign(emails: string[]) {
const results = await Promise.allSettled(
emails.map(async (email) => {
try {
const result = await resend.emails.send({ to: email, ... });
await db.emailLog.create({
email,
status: 'sent',
messageId: result.id,
});
return result;
} catch (error) {
await db.emailLog.create({
email,
status: 'failed',
error: error.message,
});
throw error;
}
})
);
const failed = results.filter(r => r.status === 'rejected');
// Retry failed sends or alert
}
Severity: WARNING
Emails should always include a plain text alternative
Message: Email being sent with HTML but no plain text part. Add 'text:' property for accessibility and deliverability.
Severity: WARNING
From addresses should come from environment variables
Message: From email appears hardcoded. Use environment variable for flexibility.
Severity: WARNING
Email bounces should be handled to maintain list hygiene
Message: Email provider used but no bounce handling detected. Implement webhook handler for bounces.
Severity: INFO
Marketing emails should include List-Unsubscribe header
Message: Marketing email detected without List-Unsubscribe header. Add header for better deliverability.
Severity: WARNING
Email sends should be queued, not blocking
Message: Email sent synchronously in request handler. Consider queuing for better reliability.
Severity: INFO
Email sends should have retry mechanism for failures
Message: Email send without apparent retry logic. Add retry for transient failures.
Severity: ERROR
API keys should come from environment variables
Message: Email API key appears hardcoded in source code. Use environment variable.
Severity: WARNING
Bulk sends should respect provider rate limits
Message: Bulk email sending without apparent rate limiting. Add throttling to avoid hitting limits.
Severity: INFO
Emails should include preview/preheader text
Message: Email template without preview text. Add hidden preheader for inbox preview.
Severity: WARNING
Email sends should be logged for debugging and auditing
Message: Email being sent without apparent logging. Log sends for debugging and compliance.
Skills: email-systems, copywriting, marketing, analytics-architecture
Workflow:
1. Infrastructure setup (email-systems)
2. Template creation (email-systems)
3. Copy writing (copywriting)
4. Campaign launch (marketing)
5. Performance tracking (analytics-architecture)
Skills: email-systems, backend, devops
Workflow:
1. Provider setup (email-systems)
2. Template coding (email-systems)
3. Queue integration (backend)
4. Monitoring (devops)
Use this skill when the request clearly matches the capabilities and patterns described above.