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email-deliverability

Email deliverability best practices and troubleshooting

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SKILL.md
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

MetricHealthyWarningCritical
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>8060-80<60

Deliverability Components

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

Sender Reputation

Warm-Up Schedule

DayEmails/DayTotal Sent
1-710-2070-140
8-1430-50280-490
15-2175-100805-1190
22-28150-2001855-2590
29+Scale gradually-

Reputation Signals

Positive SignalsNegative Signals
OpensSpam complaints
RepliesHard bounces
ClicksLow engagement
ForwardsUnsubscribes
Non-spam markingSpam 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

DoDon't
Plain text emailsHTML-heavy templates
Single link (if any)Multiple CTAs
Conversational toneSalesy language
Short sentencesLong paragraphs
Proper grammarTypos and errors

Technical Setup

Required DNS Records

RecordPurposeStatus Check
SPFAuthorize sending serversnslookup -type=TXT domain
DKIMEmail signature verificationCheck in email headers
DMARCPolicy for failed checksnslookup -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 LevelDescriptionBounce Rate
Syntax checkValid formatReduces 5-10%
Domain checkValid domainReduces 10-20%
Mailbox checkExistsReduces 20-40%
Engagement checkActiveReduces 5-15%

List Hygiene

PracticeFrequencyImpact
Remove hard bouncesImmediatelyCritical
Remove soft bouncesAfter 3 attemptsHigh
Remove unsubscribesImmediatelyCritical
Re-verify listEvery 3 monthsMedium

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

DayActionExpected Outcome
1-3Pause all sendingStop damage
4-7Remove problem addressesClean list
8-14Warm up from scratchRebuild slowly
15-21Monitor metrics closelyCatch issues early
22+Gradually scaleSustainable 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
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