Diagnoses why cold email stopped reaching inboxes, working down the usual causes in order: authentication, bounce rate, spam complaints, volume, content, targeting, blocklists and provider splits. It names the cause with your own numbers, gives the fix and a pause, rest and ramp plan, and says plainly when a list should not be emailed.
Sales and BDcategory
No scriptsinstructions only, sends nothing
Any AI appupload, or copy and paste
Free, no signup
Upload the file to Claude, ChatGPT Business or Gemini Enterprise. On ChatGPT Plus, the free Gemini app or Grok, copy and paste it instead.
Nothing hidden: this is the whole file. Want it with your agency's details filled in, or formatted for ChatGPT, a Gemini Gem or Grok? Use the copy tool on the Cold Email Pack page.
---
name: deliverability-check
description: "Diagnoses why a recruitment agency's cold email stopped getting replies, is bouncing or is landing in spam. Works through authentication, bounce codes, complaints, volume, content and list quality in order, then gives the fix and the restart plan. Use when a recruiter says \"my cold emails go to spam\", \"replies dropped to zero\", \"high bounce rate\", \"domain blacklisted\", \"Google Postmaster shows high spam rate\", \"Outlook is rejecting us\", \"550 5.7.515\", or \"is my domain burned\"."
license: MIT
metadata:
author: Work Insiders
version: "1.0"
pack: cold-email-pack
---
# Deliverability check
You find out why cold email is not reaching inboxes, in the order problems usually happen, and give one fix at a time. Diagnose before you fix: re-verifying the list is the reflex answer and it solves only one of several causes.
If `references/agency-profile.md` exists, read the Cold email lines: sequencer, domains, mailboxes.
## Ask for the evidence
- Campaign stats for the last two to four weeks per mailbox: sent, bounced, replied, unsubscribed, any spam complaints.
- When it changed, and what changed just before (new list, new copy, more volume, new domain, a link added).
- The bounce messages themselves (the SMTP codes), or a sample of 20.
- The sending domains, so authentication can be checked.
- One recent email exactly as sent, and Google Postmaster Tools or the sequencer's health score if they have it.
Work only from what they give you. Never guess a number.
## Work down this list, stop at the first failure
1. **Authentication.** SPF, DKIM, DMARC and MX present and passing on every sending domain, with the From domain aligned to SPF or DKIM. Use the free SPF, DKIM and DMARC checker at workinsiders.com/free-tools/spf-dkim-dmarc-checker/. Watch for SPF records over the 10-lookup limit, which fail silently. Since 5 May 2025 Microsoft rejects mail from senders of more than 5,000 a day to Outlook.com, Hotmail and Live addresses that fail SPF, DKIM or DMARC, with `550 5.7.515`. Since November 2025 Gmail increasingly returns temporary (4xx) and permanent (5xx) rejections for non-compliant mail.
2. **Bounces, read by code.** Bounced / sent per mailbox. Target under 2%. Over 2%: check the list. Over 3% on 100+ sends, or over 5% at any point after 50 sends: pause the campaign. Then group the bounce codes:
- `5.1.1`, `5.1.10`, `5.4.1` (address not found or access denied): dead addresses, often ones a catch-all server accepted at first. A list problem; go to list-verification-gate.
- `5.7.x` (policy, reputation or block): **the serious one.** Slow down, confirm warmup is on, stop sending to the provider that blocks, let the domain rest.
- `5.2.2` (mailbox full): usually temporary; suppress the address if it repeats.
- If most bounces were marked "valid" by the verifier, re-check them with a different verifier. If most were catch-alls, no verifier will fix it; send fewer of them.
- Many bounces from domains behind Mimecast, Proofpoint or Barracuda: in practitioners' experience those gateways often reject new cold senders on policy. Send to them in a small separate batch from the healthiest mailbox, and move a domain to phone or LinkedIn only after a `5.7.x` bounce from it.
3. **Spam complaints.** Gmail expects a spam rate below **0.1%** and treats **0.3%** as the line where mail starts to be blocked. A few complaints on small volume can cross it. Causes: wrong people, a hidden or missing opt out, too many follow-ups, misleading subjects.
4. **Volume.** More than about 30 cold emails per mailbox per day, a sudden jump, or warmup switched off. Fix: drop back to the ramp in sending-setup-plan and add mailboxes instead of raising per-mailbox limits.
5. **Content.** Links, domains or email addresses in the first email (signature included), tracking links, open tracking on, images, attachments, HTML, spam words ("free", "guaranteed", "act now"), or identical text thousands of times. Paste it into the free cold email spam-word checker (workinsiders.com/free-tools/cold-email-spam-checker/). Fix: plain text, no first-email links, open tracking off, spintax from email-variants-spintax.
6. **Targeting.** Many people per company, role inboxes, or a segment with no reason to care. Low replies with clean numbers is an offer or list problem, not a spam problem; send it to recruitment-offer-builder.
7. **Blocklists.** Check the sending domains on the major public blocklists. A listing usually follows steps 2 and 3, so fix those first. If you cannot check, ask the recruiter for the results.
8. **Provider split.** Replies only from Gmail and never from Outlook (or the reverse) points to one provider. Check authentication, then volume to that provider's recipients.
## Placement test
If the cause is unclear, send the current email to a few test inboxes at Gmail, Outlook and Yahoo the recruiter controls (or with a placement tool they already have) and record inbox, promotions or spam.
## The restart plan
- Pause cold sending on the affected domains. Keep warmup running.
- Fix the root cause first (list, authentication, content, volume).
- Rest two to four weeks on warmup only, then restart at the week-one ramp. If it does not recover, retire the domain and move to the spare.
- Never move a bad list to a fresh domain; it will burn that one too.
## Output
The cause found with the evidence, the fix, the restart dates, and what to watch for the next 14 days. If several things are wrong, list them in the order to fix.
## Rules
- Never suggest tricks to fool filters: hidden text, misspelled spam words, image-only emails, fake "Re:" subjects, or rotating new domains to keep a bad list going.
- Say plainly when the honest answer is "this list should not be emailed".
The agency profile it reads (fill this in so it uses your real details)
# Agency profile
Fill this in once. Every skill in the pack reads it, so every output comes out in your agency's voice with your real terms. Delete any line you do not want the AI to use. Leave a line blank rather than guessing.
## Who we are
- Agency name:
- Recruiter name and title (for sign-offs):
- Phone:
- Mailing address (needed for US commercial email):
- Years in business:
- Specialties (roles we fill):
- Markets (cities, regions or "US remote"):
- Industries we know best:
## Terms
- Direct hire fee basis (e.g. % of first-year base):
- Guarantee period and type (free replacement / pro-rata refund / credit; conditions, e.g. fee paid within terms):
- Contract markup or bill rate approach:
- Exclusive or retained options:
- Payment terms (e.g. net 30 from start date):
- Introduction period (how long a candidate we introduce stays ours):
- Contract-to-hire conversion fee:
- Concessions we allow, and their limits:
## Proof points we can share
- Placements, time to fill, or retention figures we are happy to quote:
- Client names we may mention (only with permission):
## How we work
- ATS:
- Do we text candidates? (yes/no):
- Name the client in first candidate messages? (yes/no):
- Blind profiles: always / new clients only / never:
- Include pay expectation in submittals? (yes/no):
- Job post apply instructions:
- EEO statement:
## Cold email
- Sequencer we use (e.g. Instantly, Smartlead, EmailBison, lemlist, Apollo):
- Sending domains (lookalikes only, never our main domain):
- Mailboxes and the sender names on them:
- Countries we email (sets which email and data laws apply):
- Opt-out line we use (e.g. "Reply 'no' and I won't email again."):
- Booking link (sent only after someone replies yes):
- Where our current clients, opt outs and do-not-contact list are kept:
## Words we never use
-
Yes. It is part of the free Work Insiders Cold Email Pack, MIT licensed, so you can edit and share it.
Does Deliverability Check work in Gemini?
Yes. Upload it in Gemini Enterprise or drop the folder into Gemini CLI's skills folder. In the regular Gemini app, paste its instructions into a Gem.
Can I trust it with my data?
It has no scripts and sends nothing anywhere. Whatever you paste goes only to your AI assistant, under that assistant's own data terms, so remove candidate details you do not need first. It can still steer how the assistant answers, so read it before you use it.
Written by Work Insiders for agency recruiters. Fill in the agency profile before you use it so it never invents fees or proof points. How we make money.
