List Hygiene
Every list, from every source, gets this pass before upload, verified or not. Three steps in order: dedup by email and by company domain, exclusion lists for customers, competitors, bounces and unsubscribes, and a mandatory MX check that silently drops any domain whose mail gateway is Mimecast or Barracuda, the two providers that reject cold mail on policy regardless of address validity.
Pipeline Playbooks · Open Source, MIT Licensed
The mandatory final pass every lead list gets before it touches a sending tool: dedup, exclusion lists, and an automatic MX check that drops Mimecast and Barracuda domains.
When to use this
- After any list export, from any source, always
- Before any upload to a sending tool, this is the gate
- Bounces are high and the list was never cleaned
- Recycling an old lead pool into a new campaign
What it covers
- Dedup by email across every source, and by company domain
- Standing exclusion files: customers, competitors, past bounces, unsubscribes, open conversations
- The mandatory MX check script and why verification cannot replace it
- Why Mimecast and Barracuda specifically get silently dropped
- Catch-all density as a diagnostic read on source quality (10-25% normal, 50%+ low quality)
- Common gotchas: per-file dedup, sampling the MX check, stale bounce files
Install just this skill
Every skill folder is self-contained. Run this from your project root to pull just this one into .claude/skills/list-hygiene/:
npx degit joelwylie7/cold-email-playbooks/.claude/skills/list-hygiene .claude/skills/list-hygiene
Want the whole system, not just one skill?
Related skills
Email Verification
Runs Kitt verification on lists you bring from elsewhere, and draws the hard line on the one mistake that costs money for nothing: re-verifying an already-verified AI Ark export.
AI Ark List Builder
Build a cold email lead list with AI Ark: precise targeting, a free preview, a mandatory back-page quality check, then a confirmed export before credits get spent.
Pre-Launch QA
A numbered gate that checks copy, settings, leads, senders, schedule and sequence structure before any campaign launches or resumes, PASS or FAIL, one line of evidence each.