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email-deliverability skill

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/plugins/instantly/skills/email-deliverability

This skill helps you optimize email deliverability by applying best practices for sender reputation, content quality, and technical setup.

npx playbooks add skill madappgang/claude-code --skill email-deliverability

Review the files below or copy the command above to add this skill to your agents.

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SKILL.md

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---
name: email-deliverability
version: 1.0.0
description: Email deliverability best practices and troubleshooting
---
plugin: instantly
updated: 2026-01-20

# Email Deliverability

## Deliverability Fundamentals

### Key Metrics

| Metric | Healthy | Warning | Critical |
|--------|---------|---------|----------|
| Bounce Rate | <2% | 2-5% | >5% |
| Spam Complaint Rate | <0.1% | 0.1-0.5% | >0.5% |
| Inbox Placement | >95% | 80-95% | <80% |
| Sender Score | >80 | 60-80 | <60 |

### Deliverability Components

```
DELIVERABILITY =
  Sender Reputation (40%)
  + Content Quality (30%)
  + Technical Setup (20%)
  + List Quality (10%)
```

## Sender Reputation

### Warm-Up Schedule

| Day | Emails/Day | Total Sent |
|-----|------------|------------|
| 1-7 | 10-20 | 70-140 |
| 8-14 | 30-50 | 280-490 |
| 15-21 | 75-100 | 805-1190 |
| 22-28 | 150-200 | 1855-2590 |
| 29+ | Scale gradually | - |

### Reputation Signals

| Positive Signals | Negative Signals |
|------------------|------------------|
| Opens | Spam complaints |
| Replies | Hard bounces |
| Clicks | Low engagement |
| Forwards | Unsubscribes |
| Non-spam marking | Spam trap hits |

## Content Quality

### Spam Filter Triggers

**High-Risk Words:**
```
FREE, GUARANTEE, WINNER, CASH, PRIZE
URGENT, ACT NOW, LIMITED TIME
Click here, Click below, Don't miss
Make money, Extra income, Work from home
```

**Formatting Red Flags:**
- ALL CAPS in subject or body
- Multiple exclamation marks!!!
- Colored fonts
- Excessive links (>1)
- Images (especially in cold email)
- Attachments

### Safe Practices

| Do | Don't |
|----|-------|
| Plain text emails | HTML-heavy templates |
| Single link (if any) | Multiple CTAs |
| Conversational tone | Salesy language |
| Short sentences | Long paragraphs |
| Proper grammar | Typos and errors |

## Technical Setup

### Required DNS Records

| Record | Purpose | Status Check |
|--------|---------|--------------|
| SPF | Authorize sending servers | `nslookup -type=TXT domain` |
| DKIM | Email signature verification | Check in email headers |
| DMARC | Policy for failed checks | `nslookup -type=TXT _dmarc.domain` |

### Recommended Settings

```
SPF: v=spf1 include:_spf.instantly.ai ~all
DKIM: Configure via Instantly dashboard
DMARC: v=DMARC1; p=none; rua=mailto:[email protected]
```

## List Quality

### Email Verification

| Verification Level | Description | Bounce Rate |
|--------------------|-------------|-------------|
| Syntax check | Valid format | Reduces 5-10% |
| Domain check | Valid domain | Reduces 10-20% |
| Mailbox check | Exists | Reduces 20-40% |
| Engagement check | Active | Reduces 5-15% |

### List Hygiene

| Practice | Frequency | Impact |
|----------|-----------|--------|
| Remove hard bounces | Immediately | Critical |
| Remove soft bounces | After 3 attempts | High |
| Remove unsubscribes | Immediately | Critical |
| Re-verify list | Every 3 months | Medium |

## Troubleshooting

### High Bounce Rate (>5%)

**Diagnosis Steps:**
1. Check bounce types (hard vs soft)
2. Identify source (specific list segment?)
3. Verify emails before adding to campaign

**Remediation:**
1. Pause campaign immediately
2. Remove all hard bounces
3. Re-verify remaining list
4. Resume with verified emails only

### Low Open Rate (<15%)

**Possible Causes:**
1. Poor sender reputation
2. Landing in spam/promotions
3. Bad subject lines
4. Wrong send time

**Diagnosis:**
1. Check sender score
2. Send test emails to Gmail/Outlook
3. Review recent changes to sending

### Spam Complaints (>0.1%)

**Immediate Actions:**
1. Pause campaign
2. Review targeting (wrong ICP?)
3. Check email frequency
4. Review unsubscribe visibility

**Long-term:**
1. Improve list sourcing
2. Better qualification
3. Add clear opt-out

## Recovery Playbook

### Reputation Recovery

| Day | Action | Expected Outcome |
|-----|--------|------------------|
| 1-3 | Pause all sending | Stop damage |
| 4-7 | Remove problem addresses | Clean list |
| 8-14 | Warm up from scratch | Rebuild slowly |
| 15-21 | Monitor metrics closely | Catch issues early |
| 22+ | Gradually scale | Sustainable growth |

### Blacklist Removal

1. Identify which blacklists (MXToolbox)
2. Fix underlying issue first
3. Request removal from each list
4. Wait 24-72 hours
5. Re-check and repeat if needed

Overview

This skill provides practical email deliverability best practices and step-by-step troubleshooting to maximize inbox placement and sender reputation. It consolidates metrics, warm-up schedules, content and technical checks, list hygiene, and recovery playbooks into actionable guidance. Use it to diagnose deliverability problems and implement fixes that reduce bounces, complaints, and blacklist risk.

How this skill works

The skill inspects four core areas: sender reputation, content quality, technical DNS/setup, and list quality. It recommends metric thresholds, a progressive warm-up schedule, high-risk content triggers, required DNS records (SPF/DKIM/DMARC), and precise remediation steps for common failures. For incidents it provides immediate actions, recovery timelines, and monitoring checkpoints to restore healthy sending.

When to use it

Launching a new sending domain or IP and need a warm-up plan.
Open rates or inbox placement drop below expected thresholds.
Bounce rate exceeds 2–5% or spam complaints rise above 0.1%.
Before large-scale campaigns to validate content and technical setup.
When recovering from a blacklist, high complaint rates, or reputation issues.

Best practices

Follow a phased warm-up: start small and scale gradually over 4+ weeks.
Keep emails plain-text, conversational, and limit links to one when possible.
Maintain SPF, DKIM, and a DMARC record and validate via DNS/header checks.
Remove hard bounces immediately and re-verify lists every three months.
Monitor key metrics daily: bounce rate, complaint rate, inbox placement, sender score.

Example use cases

New domain onboarding: apply the warm-up schedule and monitor sender score.
Troubleshooting low opens: run sender score checks, send tests to major providers, and audit subject lines.
High bounce response: pause sends, remove hard bounces, re-verify remaining addresses, then resume.
Complaint spike handling: pause campaigns, audit targeting and frequency, ensure clear unsubscribe links.
Blacklist recovery: identify lists, remediate issues, request delisting, and follow a slow warm-up post-removal.

FAQ

What bounce rate is acceptable?

Aim for under 2% as healthy; 2–5% is warning and above 5% is critical and needs immediate action.

Which DNS records are mandatory?

SPF, DKIM, and DMARC are required; verify TXT records for SPF and _dmarc and check DKIM in email headers.