Warming up a new sending domain, week by week
A volume ramp that builds reputation on a fresh domain without tripping spam filters.
A brand-new domain has no sending reputation. Send a large volume on day one and mailbox providers treat you as suspicious — because that is exactly what spammers do. Warming means starting small, sending to your most engaged recipients first, and increasing volume gradually so providers learn you are legitimate.
Before you send anything
Get the foundations right first, or warming is wasted effort:
- SPF, DKIM and DMARC published and passing — verify with our stack detector
- A dedicated sending domain or subdomain, separate from your main corporate mail
- A clean list: only recipients who genuinely opted in
The ramp
Engagement matters more than raw volume. Send to the people most likely to open and reply first — their positive signals build your reputation fastest. A typical ramp for a domain that will eventually send tens of thousands a day:
| Week | Daily volume | Send to |
|---|---|---|
| 1 | 50 → 200 | Most engaged 10% of your list |
| 2 | 200 → 1,000 | Engaged openers from the last 30 days |
| 3 | 1,000 → 5,000 | Active recipients from the last 90 days |
| 4 | 5,000 → 20,000 | Broaden to the wider active list |
| 5+ | Scale to target | Full list, minus unengaged |
Increase by roughly 2x per day within each week, not in one jump. If your metrics stay healthy, keep climbing. If they dip, hold volume steady until they recover.
What to watch
- Open rates should stay strong — you are sending to engaged people first, so anything low signals a delivery problem.
- Spam complaints must stay under 0.3%. Above that, slow down and tighten your list.
- Bounces should be minimal. High bounces mean a dirty list; verify addresses before sending.
When to add a second domain
If you run cold outbound, keep it on separate domains entirely — never warm your main domain with cold mail. One burned reputation should never take down your real customer and reply traffic. Our guide on cold email infrastructure covers that separation in depth.
Warming is patient work. Rush it and you undo weeks of progress in a single day.