madappgang/email-deliverability
plugins/instantly/skills/email-deliverability/SKILL.md
Email deliverability best practices and troubleshooting
$ install --global
skillsauthnpx skillsauth add madappgang/magus email-deliverabilityInstall this skill globally with one command. Works with Claude Code, Cursor, and Windsurf.
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TrivyContainer and dependency vulnerability scanner
95%
Clean
SemgrepStatic code analysis for vulnerabilities
95%
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mcp-scan (Snyk)Model Context Protocol security validation
95%
Skipped
Snyk (dep)Open source security scanning
50%
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Socket.devSupply chain security analysis
50%
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VirusTotalMulti-engine malware detection
50%
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CrowdStrikeAdvanced threat intelligence
50%
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OSV-ScannerOpen Source Vulnerability database check
50%
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OWASP Dep-Check
50%
Last scanned: Apr 6, 2026, 10:34 PM23.9s1 file scanned
SKILL.md
- name:
- email-deliverability
- version:
- 1.0.0
- description:
- Email deliverability best practices and troubleshooting
- user-invocable:
- false
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:
- 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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