# Cold Email Inbox Warmup

> Use this skill when new sending domains or mailboxes need warming before a cold email campaign: fresh domains, new inboxes on an existing domain, or mailboxes recovering from spam-folder placement. Produces a ramp schedule and a go/no-go check before real volume starts.

- Skill: `swan-gtm/cold-email-inbox-warmup` (Agent Skill)
- Install (CLI): `npx skillmds@latest add swan-gtm/cold-email-inbox-warmup`
- Raw SKILL.md: https://api.skillmd.com/api/skills/swan-gtm/cold-email-inbox-warmup/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Marketing & Growth
- Author: swan-gtm (https://skillmd.com/u/swan-gtm)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/swan-gtm/cold-email-inbox-warmup

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Run this before any new domain or mailbox sends cold email. It produces a ramp schedule and a clear go/no-go decision for opening campaign volume.

## The play

1. Separate the asset from the brand: cold email runs on secondary domains, never the company's primary domain. The primary's reputation is not a chip to gamble.
2. Give a fresh domain two weeks of silence after setup: authentication configured, mailboxes created, signatures and profile pictures in place, zero cold sends. Age is part of reputation.
3. Warm for at least three weeks before campaign volume: start at a handful of sends per day per mailbox, grow the daily count a little every few days, and keep replies flowing; a mailbox that only sends and never receives looks like a cannon, not a person.
4. Cap real campaign volume per mailbox at 20-30 cold sends per day, and keep warm-up activity running in the background even after campaigns start. Scale by adding mailboxes and domains, not by pushing one inbox harder.
5. Go/no-go before launch: spot-check where warm-up messages land. Anything worse than consistent inbox placement means the ramp continues; launching into the spam folder burns the list and the domain together.
6. On a placement drop or a bounce spike mid-campaign: cut volume in half, hold for several days, and only ramp back one step at a time: the same discipline as the initial warm-up, at smaller scale.

## What good looks like

- Good operators treat sending volume as something a mailbox earns, week by week; the mediocre version buys a domain on Monday and blasts 200 sends on Friday, then wonders why replies stopped.
- The tell that separates experts: they watch placement and bounce rate per mailbox, not per campaign, and they act on the first bad signal instead of the fifth.
- Consistency beats speed here exactly as on social channels: identical, boring, daily behavior is what reputation systems reward.
- Done well, every mailbox reaches campaign volume with steady inbox placement, bounce rates stay low, and a placement incident costs days, not domains.

## Rules

- MUST warm every new domain and mailbox before campaign volume; no exceptions for deadlines.
- MUST keep cold volume per mailbox at 20-30 sends per day; scale with more mailboxes, not more pressure.
- MUST keep warm-up activity running after campaigns start.
- NEVER send cold email from the primary company domain.
- NEVER keep sending through a placement drop; cut volume and re-ramp.