How to warm up a new email sending domain
A brand-new sending domain has zero reputation history. The major mail providers (Gmail, Microsoft, Yahoo) treat fresh domains with suspicion by default because spammers routinely buy throwaway domains for single-blast campaigns. Warm-up is the process of building reputation gradually so receivers learn your domain is legitimate.
The general principle
Start low, ramp gradually, prioritize engagement. The ramp curve doubles roughly every 3 to 5 days. Each batch should go to recipients most likely to open, click, and engage. Never to a cold list during warm-up.
A typical warm-up schedule (4 to 6 weeks)
| Day | Volume per day | Audience |
|---|---|---|
| 1–3 | 20–50 messages | Your most engaged subscribers (recent opens or clicks) |
| 4–7 | 100–200 messages | Recent active subscribers |
| 8–14 | 500–1,000 messages | Last 30 days active |
| 15–21 | 2,000–5,000 | Last 60 days active |
| 22–28 | 10,000–25,000 | Last 90 days active |
| 29–42 | 50,000+ | Full active list (or your normal volume) |
Adjust numbers down for smaller lists. The shape of the curve matters more than the exact volumes. Receivers watch the consistency of the ramp and the engagement quality at each step.
Prerequisites before starting warm-up
- SPF, DKIM, DMARC all configured. Sending unauthenticated mail during warm-up signals "throwaway spam domain" and destroys the curve from day 1.
- The list is verified. Bouncing on warm-up sends amplifies suspicion. See bulk verification.
- Content is genuinely good. Engagement is the most-watched signal during warm-up. Boring transactional language flagged as spammy will tank you faster than no warm-up at all.
Day-to-day monitoring
Watch four numbers daily during the ramp:
- Bounce rate. Should stay under 2% throughout. A spike means stop and verify.
- Complaint rate. Should stay under 0.1%. A spike means your content is wrong for the audience.
- Open rate. Should be above 20%, since your most engaged recipients open at high rates. A drop means either content quality or deliverability is degrading.
- Inbox placement. Periodically use a seedlist tool (GlockApps, Mail-Tester) to confirm messages are reaching inboxes, not spam folders.
If any metric goes red, pause the ramp at the current volume until it recovers. Do not double through a problem.
Common warm-up mistakes
- Starting too fast. Sending 10,000 messages on day 1 is the classic "we got blacklisted out of nowhere" story.
- Mixing in a cold list. Adds bounces and complaints just when receivers are watching most closely.
- Inconsistent days. Sending 1,000 one day, 100 the next, 5,000 the day after. Looks like a spammer testing for delivery.
- Skipping authentication. SPF/DKIM/DMARC are non-negotiable.
- Warming up two domains simultaneously from the same IP. ISPs see this as suspicious; warm one at a time.
Related questions
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