ReddRadar
Agent skill
email-deliverability
Email deliverability best practices and troubleshooting
Install this agent skill to your Project
npx add-skill https://github.com/MadAppGang/claude-code/tree/main/plugins/instantly/skills/email-deliverability
SKILL.md
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:dmarc@yourdomain.com
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:
- Check bounce types (hard vs soft)
- Identify source (specific list segment?)
- Verify emails before adding to campaign
Remediation:
- Pause campaign immediately
- Remove all hard bounces
- Re-verify remaining list
- Resume with verified emails only
Low Open Rate (<15%)
Possible Causes:
- Poor sender reputation
- Landing in spam/promotions
- Bad subject lines
- Wrong send time
Diagnosis:
- Check sender score
- Send test emails to Gmail/Outlook
- Review recent changes to sending
Spam Complaints (>0.1%)
Immediate Actions:
- Pause campaign
- Review targeting (wrong ICP?)
- Check email frequency
- Review unsubscribe visibility
Long-term:
- Improve list sourcing
- Better qualification
- 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
- Identify which blacklists (MXToolbox)
- Fix underlying issue first
- Request removal from each list
- Wait 24-72 hours
- Re-check and repeat if needed
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