Deliverability Incident Response

Things break. When they do, you need a playbook — not panic. This skill is the triage decision tree.

The five incident types

Decision tree: "my reply rate dropped"

Step 1: Quantify the drop

Was this week's reply rate < 50% of last 4 weeks' average?
  Yes → real drop, continue triage
  No  → noise, wait another week

If drop is real:

Step 2: Is it campaign-specific or fleet-wide?

Are ALL campaigns dropping, or just one?
  All → fleet-level issue (infrastructure or copy pattern)
  One → campaign-specific (targeting, copy, list)

Step 3: Fleet-wide drop — check these in order

1. Smartlead Smart Delivery spam test (/email-deliverability-audit → run-spam-test.ts)
   • If inbox placement <70% → real deliverability issue, skip to Step 4
   • If inbox placement >85% → deliverability is fine, look at copy/targeting instead
2. Check domain authentication (/email-deliverability-audit → check-domain-auth.ts)
   • Missing DKIM on any domain → fix immediately (see /zapmail-domain-setup-public for reconnect steps)
   • DMARC policy=reject with alignment failures → temporarily lower to quarantine
3. Check warmup status (/smartlead-inbox-manager → list-health.ts)
   • If multiple inboxes blocked in warmup → warmup network flagged you
   • If reputation dropped "good" → "fair" on many inboxes → slow down sending volume
4. Check bounce rate (/email-deliverability-audit → audit-performance.ts)
   • If bounce >3% → list quality degraded
   • If bounce <1% but reply rate low → emails landing in spam (Step 1 result)

Step 4: You have a spam-placement problem — what to do

Time-ordered actions:

1. Immediate (today): Pause the highest-volume campaign. Stop damage.
2. Day 1: Run spam placement test on 2-3 sender subsets (tag=active vs tag=new). Find which cohort is worst.
3. Day 1: Check the spam-filter-details report from Smart Delivery — specifically which filters are firing. Common: DKIM_INVALID, HTML_MESSAGE, LINK_REDIRECT. Each has a specific fix.
4. Day 2: Fix the identified issues:
   • DKIM_INVALID → verify DKIM records across all domains, re-publish if needed
   • HTML_MESSAGE → simplify email body (fewer fonts, no inline CSS, no tracking pixels)
   • LINK_REDIRECT → remove or reduce links in email 1 (ideally 0 links)
5. Day 3-14: Slow down send volume. Cut daily send per inbox by 50% for a week. Reputation rebuilds slowly.
6. Day 14: Re-test spam placement. If back above 85% → resume normal volume.

Decision tree: "bounce rate spiked"

Step 1: What kind of bounces?

Smartlead categorizes bounces as hard (invalid address) or soft (temporary).

bounce_rate > 3% AND mostly_hard_bounces
  → list quality problem, verify with MillionVerifier

bounce_rate > 3% AND mostly_soft_bounces (greylist, temp)
  → domain reputation problem, slow sending

bounce_rate > 5% either type
  → stop the campaign immediately to prevent ISP suspension

Step 2: If list problem

1. Export remaining leads from the campaign
2. Run through MillionVerifier (batch, ~$2 per 1,000)
3. Only reuse emails with status "ok"
4. Discard the rest

Step 3: If reputation problem

Slow way down. Cut daily volume 50% per inbox for 2 weeks. Run warmup more aggressively.

Decision tree: "domain blacklisted"

Step 1: Confirm the blacklist

Check:

• Spamhaus, Barracuda, SURBL via /email-deliverability-audit → spam-test report → blacklist detail
• MX Toolbox (https://mxtoolbox.com/blacklists.aspx) for a second opinion

Step 2: What tier of blacklist?

• Domain on Spamhaus DBL or SURBL → serious. You may need to replace the domain entirely.
• Sending IP on a DNSBL → usually the IP pool's fault (not yours, if on Zapmail shared IPs). Zapmail rotates IPs; wait 1-2 weeks.
• Minor list (e.g., Barracuda) → submit delisting request at their portal. Usually resolved in 3-7 days.

Step 3: Replace vs repair

• Domain <30 days old + blacklisted → replace. Not worth the cleanup effort.
• Domain >90 days old + blacklisted → try repair. Stop sending for 7 days, submit delisting requests, slowly resume.
• If you replace: archive the old domain, buy a new lookalike via /zapmail-domain-setup-public, warm it for 2 weeks before reusing.

Decision tree: "inbox blocked in warmup"

Step 1: Why is it blocked?

Smartlead's is_warmup_blocked: true flag usually means:

• Your warmup emails looked like spam to the warmup network
• Too many warmup peers marked them as spam
• The inbox type/provider is rate-limiting

Step 2: Triage

1. Check the blocked_reason field (if populated)
2. If warmup network issue → the inbox reputation may be damaged. Cost-benefit:
   • Young inbox (<30 days) → retire, provision new
   • Established inbox (>90 days, previously good reputation) → try disabling and re-enabling warmup with lower total_warmup_per_day (try 15 instead of 40)
3. If ISP rate-limit → wait 48h, re-enable warmup

Step 3: Retire workflow (via /smartlead-inbox-manager)

# Tag as retired
npx tsx scripts/tag-inboxes.ts --ids=<id> --add-tag=retired --remove-tag=active

# Disable warmup
npx tsx scripts/set-warmup.ts --mode=disable --ids=<id>

# Replace — buy new domain, create new inbox
# See /zapmail-domain-setup-public

Decision tree: "Gmail marking as promotional"

Step 1: Test on a fresh Gmail account

Send the campaign's email 1 to a fresh @gmail.com account (yours, not in the campaign). Where does it land?

• Primary → you're fine
• Promotions → this is the issue
• Spam → you have a bigger deliverability problem (see above)

Step 2: Promotional-tab triggers (and fixes)

• Multiple links in email → drop to 0-1 links in email 1
• Images / inline images → remove them
• Heavy HTML styling → simplify, fewer tags
• Marketing-style phrases ("click here", "act now", "limited time") → remove
• Unsubscribe in header (List-Unsubscribe) — actually helps deliverability, but formatting must be correct
• Mass signature blocks with logos → simplify to text-only

Step 3: A/B test

Create two versions — your current and a stripped-down version. Send 50 leads each. Check which has better reply rate after 7 days.

The 72-hour "total failure" checklist

If NOTHING is working and you don't know why:

1. Pause all campaigns. Stop damage.
2. Audit: run /email-deliverability-audit full suite
3. Spam test: run Smart Delivery on 2 sender subsets
4. Check SPF/DKIM/DMARC on every domain — if ANY are missing, fix before resuming
5. Check Zapmail health dashboard — if their IPs are in trouble, everyone on their pool is too
6. Reduce volume 75% for the restart
7. Use a known-good copy — don't launch new copy during recovery
8. Watch reply rate daily for 7 days post-restart

When to call in experts

• You've been in spam for >2 weeks despite fixes → infrastructure level issue, consider migrating sending platforms
• Multiple domains permanently blacklisted → IP pool issue, switch providers
• Domain reputation never recovers after 4 weeks → retire domain, replace

What to do next

Re-run /email-deliverability-audit --days=7 in 7 days to confirm recovery. Domain/inbox reputation rebuilds slowly — don't re-audit before the 7-day window.

Meanwhile: continue the weekly rhythm via /cold-email-weekly-rhythm, which catches new issues as they emerge.

Or wait: if the incident required replacing domains/inboxes, wait 2 weeks for warmup on the replacements before expecting full recovery.

Related skills

• /email-deliverability-audit — the diagnostic suite you run first
• /smartlead-inbox-manager — tag, rotate, retire inboxes
• /zapmail-domain-setup-public — replace a burned domain
• /positive-reply-scoring — confirm recovery (reply rate back to baseline)

The 1% rule sanity check

After fixes, give it at least 200 sends at your normal volume. If reply rate is still <1% — there's a deeper issue. Start the playbook over.