Domain warm-up plan
You set up new domains or mailboxes for cold email and need a warm-up plan.
You get Setup checklist · Week-by-week ramp · Health gates
Deliverability audit Claude skill
Use this when results drop and the copy has not changed. Most "the campaign stopped working" problems are deliverability problems: the emails are not being seen.
- 7-step play
- 4 guardrails
- 2 files
- Human approval built in
Use it when cold emails land in spam or reply rates suddenly drop.
Then just ask your agent
“Our reply rate went from 4% to 0.5% in two weeks. Audit our deliverability.”
Watch it work
One request in, expert work out
What happens when you ask your agent with this skill installed. Every step below comes straight from the skill.
You
Our reply rate went from 4% to 0.5% in two weeks. Audit our deliverability.
Loaded skill
deliverability-audit- Check authentication
- Check the domain strategy
- Check volume and pattern
- Check list quality
- Check content
Ranked problems · Fix plan · Recovery timeline
Ready for your review. Nothing is sent or changed until you approve.
- 7Steps in the play
- 4Guardrails
- 2Files in the skill
- 4 minTo read it all
What good looks like
- Diagnosis by mailbox and domain, not just campaign averages; one bad mailbox can hide inside a healthy average.
- The fix plan pauses damaged mailboxes rather than pushing more volume through them.
- The common mistake is rewriting copy for weeks while the real cause is a missing DMARC record or a 6% bounce rate.
What you bring
- Sending domains and mailboxes
- DNS records
- Campaign metrics
- Sample emails
What you get
- Ranked problems
- Fix plan
- Recovery timeline
- Monitoring checklist
name:deliverability-audit
description:Use this skill when cold emails land in spam or reply rates suddenly drop: "audit my email deliverability", "why are my emails going to spam", "check my sending setup", "open and reply rates fell…
Use this when results drop and the copy has not changed. Most "the campaign stopped working" problems are deliverability problems: the emails are not being seen.
Inputs
- Sending domains and the number of mailboxes on each.
- DNS records (SPF, DKIM, DMARC, MX) or permission to look them up.
- Metrics per mailbox: volume per day, bounce rate, reply rate, spam complaints, over the last 30-60 days.
- Two or three sample emails as sent.
The play
1. Check authentication
SPF, DKIM and DMARC must exist, align with the From domain, and pass. Large mailbox providers require all three for bulk senders and reject or junk unauthenticated mail. Read references/audit-checklist.md for the full checklist and what each failure looks like.
2. Check the domain strategy
- Cold email from the primary company domain risks the domain that carries invoices and customer mail. Use separate, aged sending domains that redirect to the main site.
- Each sending domain has 2-5 mailboxes, not 20.
- A custom tracking domain, or no open and click tracking at all for cold outreach.
3. Check volume and pattern
- Per mailbox: 30-50 cold emails a day after warm-up is a common safe range.
- Sending spread through the working day, not in one burst.
- Sudden jumps in volume (doubling overnight) are a common trigger for filtering.
4. Check list quality
Bounce rate over 2-3% means a list problem. Spam complaints over 0.1% (one in a thousand) are a red flag; 0.3% is the threshold large providers warn about. Old lists, purchased lists and catch-all-heavy lists are usual causes.
5. Check content
Links (especially link shorteners), images, attachments, tracking pixels, spam-pattern words and heavy HTML all add risk. Cold email should be plain text-looking with zero or one link.
6. Test placement
Send to a seed set of test inboxes across providers, or ask friendly contacts to check folders. Separate "inbox", "promotions or other" and "spam".
7. Rank and fix
Order fixes by impact: authentication failures and blacklisting first, then list quality, then volume, then content.
Output format
Verdict: healthy / at risk / damaged
Problems (ranked): <issue - evidence - impact - fix>
Recovery plan: <week by week>
Monitor weekly: bounce %, complaint %, reply rate per mailbox, placement testWhat good looks like
- Diagnosis by mailbox and domain, not just campaign averages; one bad mailbox can hide inside a healthy average.
- The fix plan pauses damaged mailboxes rather than pushing more volume through them.
- The common mistake is rewriting copy for weeks while the real cause is a missing DMARC record or a 6% bounce rate.
Rules
- MUST check authentication before content.
- MUST recommend pausing any mailbox with bounces over 5% or complaints over 0.3%.
- NEVER recommend tactics that disguise the sender or evade provider filters (hidden text, misleading headers, rotating look-alike domains to dodge complaints).
- NEVER change DNS records without the user’s approval.
Example prompts
- "Our reply rate went from 4% to 0.5% in two weeks. Audit our deliverability."
- "Here are our DNS records and per-mailbox stats. What’s wrong?"
- "Build a deliverability checklist we run before every campaign."
Deliverability audit checklist
Authentication
| Check | Pass | Common failure |
|---|---|---|
| SPF record exists | One TXT record starting v=spf1 | Two SPF records (invalid), or missing |
| SPF lookups | 10 DNS lookups or fewer | Too many includes → permerror |
| SPF covers the sender | Sending service included | Mail sent by a tool not listed |
| DKIM | Signing enabled, key published, passes | Key published but signing not turned on |
| DMARC | v=DMARC1 record at _dmarc.domain | Missing, or invalid syntax |
| Alignment | From domain aligns with SPF or DKIM domain | Sending service signs with its own domain |
| Reverse DNS / sending infrastructure | Handled by the mailbox provider | Self-hosted servers without PTR |
Domain and mailbox setup
- Sending domains separate from the primary domain for cold volume.
- Domains older than 30 days before cold sending; warmed for 2-4 weeks.
- 2-5 mailboxes per domain.
- Real names on mailboxes, profile photos, a signature with company details.
- Sending domain redirects to the main website.
- Custom tracking domain if tracking is used.
Metrics thresholds (per mailbox, 7-day window)
| Metric | Healthy | Warning | Stop |
|---|---|---|---|
| Bounce rate | < 2% | 2-5% | > 5% |
| Spam complaints | < 0.1% | 0.1-0.3% | > 0.3% |
| Reply rate | > 3% | 1-3% | < 1% sustained (check placement) |
| Daily volume | Within plan | +50% jump | Doubling overnight |
Content risks
- More than one link, link shorteners, links to new or low-reputation domains.
- Images, attachments, heavy HTML templates.
- Open tracking pixel on cold email.
- Spam-pattern words, all caps, many exclamation marks.
- Identical copy to thousands of recipients (use variation).
Recovery timeline for a damaged mailbox
| Week | Action |
|---|---|
| 1 | Pause cold sending; fix authentication and list issues; keep warm-up running |
| 2 | Resume at 10-15 cold emails a day to the best-fit, verified contacts |
| 3 | 20-25 a day if bounces < 2% and no complaints |
| 4+ | Back to normal volume if placement tests show inbox |
If a domain is listed on major blocklists or placement stays in spam after four weeks, retire it and move volume to healthy domains gradually.
Try it
Ask your agent like this
Once the skill is installed, plain requests like these load it automatically. Swap in your own company, buyer and numbers.
-
“Our reply rate went from 4% to 0.5% in two weeks. Audit our deliverability.”
-
“Here are our DNS records and per-mailbox stats. What's wrong?”
-
“Build a deliverability checklist we run before every campaign.”
What does the Deliverability audit skill do?
Use this when results drop and the copy has not changed. Most "the campaign stopped working" problems are deliverability problems: the emails are not being seen. You get: ranked problems, fix plan, recovery timeline, monitoring checklist.
When should I use the deliverability audit skill?
Use it when cold emails land in spam or reply rates suddenly drop.
How do I install Deliverability audit in Claude Code?
Run /plugin marketplace add prosyo-ai/gtm-skill and then /plugin install gtm-skills@prosyo to add the whole library, or run npx skills add prosyo-ai/gtm-skill –skill deliverability-audit for this skill alone. In Claude.ai, download the .zip from this page and upload it under Settings, Capabilities, Skills.
What do I need to give the agent?
Have these ready: sending domains and mailboxes, dns records, campaign metrics, sample emails. If something is missing, the skill tells the agent to ask for it rather than guess.
Does it work with ChatGPT, Codex, Cursor or Gemini?
Yes. The skill is a plain SKILL.md file with no vendor lock-in. Agents that load skills natively (Claude Code, Claude.ai, Codex, Cursor, Gemini CLI and others) pick it up automatically; anywhere else, paste the file into the conversation as instructions.
Will it send emails or messages on its own?
No. Every skill in the library drafts, researches and analyses, and waits for a person to approve anything that sends, schedules or changes records in bulk. Your inbox, CRM and accounts stay under your control.
Is it free, and can I change it?
Yes. It is free and MIT-licensed. Copy it, adapt it to your market and voice, and if you improve it, open a pull request so everyone gets the better version.
Keep going
Browse all 69 skills
Skills that pair well with this one
Sending capacity planner
You need to know how many mailboxes, domains and LinkedIn accounts a meeting target requires, or how much a team can safely send.
You get Contacts and sends needed · Mailboxes domains and accounts needed · Ramp timeline
SPF, DKIM and DMARC setup
You need to set up or fix SPF, DKIM and DMARC for a sending domain.
You get Sender inventory · Exact DNS records · DMARC rollout plan
Open source
Have a play that works? Share it as a skill.
Paste this into Claude, Codex or any agent. It interviews you about your play, writes the skill in the house format, checks it and opens the pull request. Once it is merged, it shows up here with your name on it.
Prompt for your agent
Fetch https://raw.githubusercontent.com/prosyo-ai/gtm-skill/main/AGENTS.md and follow its submission flow. Interview me about my GTM play (the real numbers, rubrics and examples), draft it in their format with reference pages, validate it and open the pull request.
Two ways to run it
Run it yourself, or put it on autopilot
The skill gives your agent the playbook. Penny, the Prosyo AI SDR, runs plays like this for you every day across LinkedIn and email.
Free · this skill
You and your agentBest for trying the play and one-off work
- Your agent follows the deliverability audit playbook step by step
- You bring the inputs and run it when you need it
- Works in Claude, Codex, Cursor and 40+ agents
- You review every draft before it goes anywhere
Prosyo AI SDR
Penny runs it for youBest for a pipeline that grows every day
- Finds the right buyers for your ICP every day
- Writes from what each prospect actually posted
- Follows up on LinkedIn and email at a safe, human pace
- Every reply lands in one inbox with an answer drafted
- You approve what goes out
Skills draft the play. Penny runs it.
Penny, the Prosyo AI SDR, finds your buyers, writes from what they actually posted, follows up on LinkedIn and email and lands every reply in one inbox with an answer ready. 7 days free, no card.
- 7 days free
- No card required
- Cancel in two clicks
