Agent Skills: Email Deliverability

Email deliverability best practices and troubleshooting

UncategorizedID: madappgang/claude-code/email-deliverability

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plugins/instantly/skills/email-deliverability/SKILL.md

Skill Metadata

Name
email-deliverability
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: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:

  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