---
name: "Email deliverability audit"
repo: https://github.com/growthenginenowoslawski/coldoutboundskills
source: https://github.com/growthenginenowoslawski/coldoutboundskills/blob/HEAD/skills/email-deliverability-audit/SKILL.md
license: "MIT"
install: "npx skills add growthenginenowoslawski/coldoutboundskills --skill email-deliverability-audit"
page: https://100xlab.com/resources/agent-skills/growthenginenowoslawski-coldoutboundskills--email-deliverability-audit--1atqlrw
---

# Email Deliverability Audit

**If your positive reply rate is dropping and you don't know why, start here.** Most of the time the problem is deliverability — your emails aren't reaching inboxes. This skill tells you what's broken.

## What it checks

| Layer | What | How |
|---|---|---|
| DNS auth | SPF, DKIM, DMARC present on each sending domain | `dig` commands |
| Inbox health | Warmup status, reputation, blocks, connection failures | Smartlead email-accounts API |
| Volume health | Daily sent trending, capacity utilization | Smartlead analytics |
| Send + reply rate per inbox | Sent count, reply count, reply rate % over lookback period | Smartlead campaign analytics |
| Bounce rate | Per-inbox and per-domain bounce rate over last 30 days | Smartlead campaign analytics |
| Spam placement | Real inbox-vs-spam test via Smartlead Smart Delivery | optional |

## The 1% rule — core domain-health threshold

**A healthy domain should have an overall reply rate of at least 1% after 200 emails sent.**

Below 1% after 200+ sends is a red flag — something is broken. The audit explicitly checks this and flags any domain or inbox that:
- Has sent ≥200 emails in the lookback window
- Has an overall reply rate <1%

Possible causes (the audit's "root-cause suggestions" try to pinpoint which):
- Emails landing in spam (run the spam placement test)
- Domain reputation damaged (check DMARC reports, reconsider domain age)
- Copy is broken (manually review for vague CTAs, generic openers, or em dashes; re-run `/spam-word-checker`)
- List is cold / wrong ICP (check bounce rate — if >3%, list is the problem)
- Inbox hasn't warmed enough (check warmup status)

Below 200 sends: too early to judge. The rule needs sample size.

## When to use

- Reply rate dropped by >30% week-over-week → run the full audit
- Bounces spiked above 2% → run auth + spam-placement checks
- Before scaling a campaign (make sure infrastructure is ready)
- Monthly as routine hygiene
- When taking over a Smartlead account you didn't set up

## Inputs

- `SMARTLEAD_API_KEY` (env)
- Optional: scope the audit
  - `--client-id=X` (for sub-clients)
  - `--campaign-id=X` (audit only one campaign's inboxes)
  - `--domain=example.com` (audit only one domain)
  - `--tag=active` (audit only inboxes tagged active)

## Steps

### 1. Pull the inbox inventory

```bash
npx tsx scripts/audit-inboxes.ts --all --out=/tmp/audit/inboxes.csv
```

Outputs per inbox: id, email, domain, warmup_status, reputation, max_warmup/day, sent_today, smtp_ok, imap_ok, is_blocked, tags.

### 2. Check domain authentication

```bash
npx tsx scripts/check-domain-auth.ts --from-csv=/tmp/audit/inboxes.csv --out=/tmp/audit/auth.csv
```

For each unique domain, runs:
```bash
dig TXT <domain> +short          # SPF
dig TXT default._domainkey.<domain> +short    # DKIM (Zapmail uses "default")
dig TXT _dmarc.<domain> +short   # DMARC
```

Outputs: domain, spf_present, spf_strict, dkim_present, dmarc_present, dmarc_policy (none/quarantine/reject).

### 3. Pull sent + reply + bounce metrics per campaign/inbox

```bash
npx tsx scripts/audit-performance.ts --days=30 --out=/tmp/audit/performance.csv
```

Walks all active campaigns, pulls per-inbox analytics for the last 30 days. Output columns: `inbox_id, email, domain, type, tags, sent, replies, bounces, reply_rate_pct, bounce_rate_pct, flag_low_reply, flag_high_bounce`.

Flagged automatically:
- **`flag_low_reply = TRUE`** if sent ≥200 and reply_rate_pct < 1.0 (the 1% rule)
- **`flag_high_bounce = TRUE`** if sent ≥50 and bounce_rate_pct > 3.0

### 4. (Optional) Run a Smart Delivery spam placement test

```bash
npx tsx scripts/run-spam-test.ts --campaign-id=12345 --senders=100 --out=/tmp/audit/spam-test.json
```

This creates a real inbox-placement test via Smartlead's Smart Delivery API:
- Uses the only available provider pools: G Suite + Office365 (provider_ids 20, 21)
- Sends to ~200 seed mailboxes with 100 of your senders
- Waits for completion (5-20 min)
- Pulls: providerwise, spam-filter-details, dkim-details, spf-details, blacklist

Output shows: what % lands in Inbox vs Spam vs Promotions, broken down by your sender and the receiver provider. This is the ground truth.

### 5. Synthesize the report

```bash
npx tsx scripts/generate-report.ts --audit-dir=/tmp/audit --out=/tmp/audit/report.md
```

Produces a markdown report like:

```
# Deliverability Audit — 2026-04-17

## Summary

- 80 inboxes audited across 40 domains
- 3 inboxes blocked (4% of fleet)
- 5 domains missing DKIM
- 2 domains with DMARC policy=none (no enforcement)
- Fleet performance (last 30d):
    Sent:           42,384
    Replies:          523
    Overall reply rate: 1.23% (PASS — above 1% threshold)
    Bounces:           382
    Bounce rate:      0.90% (PASS — below 2%)
- 4 inboxes failed the 1% rule (sent ≥200, reply rate <1%)
- Spam placement (test run): 83% inbox / 14% spam / 3% tabs (ACCEPTABLE but not great)

## Critical issues (fix within 24h)

1. Domain trygrowth.co has no DMARC record. Add: v=DMARC1; p=none; rua=mailto:dmarc@trygrowth.co
2. Inbox sales@trygrowth.co blocked in warmup — likely flagged by warmup network. Rotate out of campaigns.
3. 12 inboxes have 0 daily sent today despite being in active campaigns. Check campaign schedule.
4. Inbox marketing@other.co failed the 1% rule: 347 sent, 1 reply (0.29% reply rate). Investigate:
   - Check spam placement for this inbox
   - Compare copy vs. a sibling inbox that's passing
   - Rotate inbox out if bad reputation is confirmed

## Warnings (fix within 1 week)

- 5 domains missing DKIM record at default._domainkey
- 3 inboxes reputation dropped "fair" → "bad"
- Spam filter trigger DKIM_INVALID firing 8% of the time — likely for a subset of domains

## Action items (prioritized)

1. [HIGH] Add missing DKIM records to: trygrowth.co, othergrow.co, ...
2. [HIGH] Rotate out blocked inboxes: sales@trygrowth.co, marketing@other.co, ...
3. [MED] Tighten DMARC to p=quarantine on all domains after 2 weeks of p=none observation
4. [MED] Replace 3 bad-reputation inboxes (tag them "retired", provision new)
5. [LOW] Re-run spam placement test after fixing DKIM issues
```

### 6. Act on the action items

Feed the action items into the right skills:
- Missing DKIM / SPF → `/zapmail-domain-setup-public` to reconnect domains through Zapmail
- Blocked inboxes → `/smartlead-inbox-manager` to tag "retired" and rotate in insurance
- Campaign schedule issues → Smartlead campaign schedule settings
- Bad copy flagged → `/spam-word-checker` on the campaign copy

## Interpreting the numbers

### Bounce rates
- **<1%** — Excellent. Healthy list.
- **1-2%** — Normal for cold. No action.
- **2-3%** — Yellow. Check list quality, might be old emails.
- **>3%** — Red. Verify the list (MillionVerifier), consider pausing.
- **>5%** — Stop immediately. You're damaging domain reputation.

### Spam placement
- **>90% inbox** — Great. Ship more.
- **80-90% inbox** — Acceptable.
- **70-80% inbox** — Yellow. Look at spam-filter-details to see what's triggering.
- **<70% inbox** — Red. Pause and fix auth + copy before sending more.

### DMARC policies
- **None** — Acceptable for first 2 weeks of a domain's life. After that, tighten.
- **Quarantine** — Recommended long-term. Emails that fail auth land in spam.
- **Reject** — Strictest. Only use after 30+ days of clean `rua=` reports confirming all legitimate mail passes.

### Warmup reputation
- Smartlead reports reputation as 0-100 internally. Higher is better.
- Above 80: inbox is good to send from.
- 50-80: keep warming, don't use for critical sends.
- Below 50: don't send from this inbox — warmup peers aren't seeing it in their inboxes.

## Common root causes

- **SPF too lax** — `v=spf1 +all` whitelists everyone. Use `v=spf1 include:zapmail.com ~all` or similar.
- **DKIM missing** — new domain, selector not published. Zapmail publishes at `default._domainkey` by default.
- **DMARC alignment failure** — From-domain doesn't match SPF/DKIM domain. Usually a misconfigured reply-to or a 3rd-party sender.
- **Too many inboxes per domain** — Gmail flags domains with >3-5 inboxes as suspicious. Keep it at 2/domain.
- **Aggressive warmup ramp** — Jumping from 5 to 40/day in one week = flag. Ramp over 2-4 weeks.
- **Shared sending IP with spam traffic** — Zapmail/most providers use shared pools. If someone else on your IP spammed, you suffer. Not much to do except wait for pool rotation.

## What to do next

**If any flag fired:** `/deliverability-incident-response` → triage decision tree for whatever was flagged (low reply rate, high bounce, blocked inbox, etc).

**If all clean:** next Monday, run this again. This audit is the Monday task in `/cold-email-weekly-rhythm`.

**Or wait:** if you just applied fixes, wait 7 days then re-audit. Reputation changes propagate slowly.

## Related skills

- `/smartlead-inbox-manager` — execute the action items (rotate, retag, warmup settings)
- `/zapmail-domain-setup-public` — fix DNS/auth issues at the domain provider
- `/spam-word-checker` — check copy for spam-triggering phrases
- `/deliverability-test-public` — lighter-weight SMTP vs Gmail vs Outlook reply/bounce comparison

## Scripts

- `scripts/audit-inboxes.ts` — pull + format inbox inventory
- `scripts/check-domain-auth.ts` — dig-based SPF/DKIM/DMARC checks
- `scripts/audit-performance.ts` — per-inbox sent / replies / bounces / rates from campaign analytics (applies the 1% rule)
- `scripts/run-spam-test.ts` — create + poll + pull Smart Delivery test
- `scripts/generate-report.ts` — synthesize all CSVs into markdown report
- `scripts/_smart-delivery.ts` — shared Smart Delivery API wrapper

## References

- `references/smart-delivery-api.md` — full endpoint reference for Smart Delivery
- `references/dns-records.md` — SPF/DKIM/DMARC record templates + interpretation guide

---

## Supporting file: references/dns-records.md

# DNS Records for Cold Email Deliverability

Three records every sending domain needs: **SPF, DKIM, DMARC**. Miss any one and your deliverability suffers.

## SPF (Sender Policy Framework)

Declares which servers are allowed to send mail on behalf of your domain.

**Record type:** TXT
**Host:** `@` (the bare domain, e.g. `example.com`)
**Value format:**
```
v=spf1 include:<provider> ~all
```

### Examples

| Provider | SPF value |
|---|---|
| Zapmail | `v=spf1 include:_spf.zapmail.com ~all` |
| Google Workspace | `v=spf1 include:_spf.google.com ~all` |
| Microsoft 365 | `v=spf1 include:spf.protection.outlook.com ~all` |
| SendGrid | `v=spf1 include:sendgrid.net ~all` |

### Strictness modifiers

- `~all` (soft fail) — emails that fail get marked suspicious but usually still delivered. **Default for new domains.**
- `-all` (hard fail) — emails that fail get rejected. **Only use after weeks of clean mail.**
- `+all` — allows any sender. **NEVER use. Makes SPF useless.**
- `?all` — neutral. Same as no SPF.

### Verify
```bash
dig TXT example.com +short | grep spf1
```

## DKIM (DomainKeys Identified Mail)

Cryptographic signature that proves the email wasn't modified in transit.

**Record type:** TXT
**Host:** `<selector>._domainkey` (e.g. `default._domainkey` for Zapmail, `google._domainkey` for Workspace)
**Value:** Long public key provided by your sending provider. Looks like:
```
v=DKIM1; k=rsa; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC...
```

### Zapmail default selector
Zapmail publishes DKIM at the `default` selector. Check with:
```bash
dig TXT default._domainkey.example.com +short
```

### Workspace selector
`google._domainkey.example.com`

### Microsoft 365 selectors
`selector1._domainkey.example.com` and `selector2._domainkey.example.com`

### Why it's often missing
- Domain wasn't connected through the sending provider's onboarding flow
- Selector published on old provider, domain migrated without re-publishing
- Propagation not yet complete (wait up to 48h after setup)

## DMARC (Domain-based Message Authentication, Reporting and Conformance)

Tells receiving servers what to do with emails that fail SPF/DKIM, and where to send reports.

**Record type:** TXT
**Host:** `_dmarc`
**Minimum value:**
```
v=DMARC1; p=none; rua=mailto:dmarc@example.com
```

### Policy levels

- `p=none` — monitor only. Failing emails still delivered. Reports sent to `rua=` address. **Start here.**
- `p=quarantine` — failing emails go to spam. **Upgrade to this after 1-2 weeks of clean `rua=` reports.**
- `p=reject` — failing emails bounced. **Strictest. Use only after 30+ days confirmed clean.**

### Additional tags

```
v=DMARC1; p=quarantine; rua=mailto:dmarc@example.com; ruf=mailto:forensic@example.com; pct=100; adkim=r; aspf=r
```

- `rua` — aggregate reports (daily summary). Set this.
- `ruf` — forensic reports (per-failure detail). Optional, gets noisy.
- `pct` — percentage of failing mail to apply policy to. Start at 100.
- `adkim=r|s` — DKIM alignment mode. `r` = relaxed (subdomain OK), `s` = strict.
- `aspf=r|s` — SPF alignment mode. Same as above.

### Verify
```bash
dig TXT _dmarc.example.com +short
```

## Checklist for a new domain

1. **Day 0 — registration:** point nameservers to your sending provider (e.g., Zapmail)
2. **Day 0-1 — DNS propagation:** wait 20 min - 48h for records to appear
3. **Day 1 — verify all three:**
   ```bash
   dig TXT example.com +short
   dig TXT default._domainkey.example.com +short
   dig TXT _dmarc.example.com +short
   ```
4. **Day 1-14 — warmup:** DMARC `p=none`, SPF `~all`. Warm inboxes slowly.
5. **Day 14 — tighten DMARC:** switch to `p=quarantine` if aggregate reports are clean.
6. **Day 30+ — optional reject:** switch to `p=reject` if you're confident no legitimate mail will fail.

## Common failure patterns

| Symptom | Likely cause |
|---|---|
| SPF present but marked soft-fail in DMARC reports | SPF `include:` list missing your provider |
| DKIM signature in email but DMARC still fails | From-domain doesn't match DKIM-signing domain (alignment issue) |
| DMARC reports show failures from your own sending | DKIM selector moved or expired |
| Emails landing in spam despite all 3 passing | Domain reputation issue — content/behavior, not auth |
| Brand-new domain, all auth fails | DNS propagation still in progress, wait 48h |

## How Zapmail handles this

Zapmail's onboarding flow typically publishes SPF, DKIM, and DMARC (`p=none`) automatically when you connect a domain to them. If any are missing:
- Re-run Zapmail's "verify domain" wizard
- Check the nameservers actually point to Zapmail
- Wait longer for DNS propagation

If you need more control, switch to "custom DNS" mode in Zapmail and publish records manually at your registrar.