Email Warmup: why new domains land in spam and a step-by-step warmup plan
Email warmup is the process of gradually increasing send volume from a new domain or IP to build sender reputation. Here's a 4-week plan with daily volumes.
Email warmup is the process of gradually increasing the number of emails you send from a new domain or IP address, so email providers like Gmail and Outlook build trust in you as a sender.
A brand new domain has no reputation. No history. To Gmail, you’re a complete unknown — and unknown senders who suddenly send thousands of emails are suspicious by definition. That’s spam behavior.
Why warmup is necessary
Email providers use sender reputation to decide whether your emails reach the inbox or the spam folder. Google Postmaster Tools lets you monitor your domain reputation with Gmail during warmup. Reputation builds over time based on:
- Volume and consistency — gradual, predictable increases are good. Sudden spikes are bad.
- Engagement — recipients who open, click, and reply strengthen your reputation. Recipients who mark you as spam destroy it.
- Bounce rate — low bounce rate signals a clean list. High bounce rate signals spam.
- Spam complaints — above 0.1% spam complaint rate is a red flag for most providers, as stated in Google’s sender guidelines.
Warmup is about demonstrating all four signals positively from the start.
4-week warmup plan
This plan assumes a new domain with a dedicated IP. If you use shared IP, you can increase slightly faster.
Week 1: Foundation (20-100 emails/day)
| Day | Daily volume |
|---|---|
| 1-2 | 20 |
| 3-4 | 50 |
| 5-7 | 100 |
Send only to your most engaged contacts — those you know open and click. Their positive engagement builds your initial reputation.
Week 2: Building (100-500 emails/day)
| Day | Daily volume |
|---|---|
| 8-9 | 200 |
| 10-11 | 300 |
| 12-14 | 500 |
Expand to contacts who opened emails within the last 30 days. Monitor bounce rate and spam complaints daily.
Week 3: Acceleration (500-2,000 emails/day)
| Day | Daily volume |
|---|---|
| 15-16 | 750 |
| 17-18 | 1,000 |
| 19-21 | 2,000 |
Include contacts with engagement within 60 days. If your bounce rate stays below 2% and spam complaints below 0.1%, you’re on track.
Week 4: Full capacity (2,000+ emails/day)
| Day | Daily volume |
|---|---|
| 22-24 | 3,000 |
| 25-28 | 5,000+ |
Gradually increase to your normal sending pattern. Continue monitoring metrics.
Dedicated vs shared IP
Shared IP — you share an IP address with other senders on the platform. Their reputation affects yours, but you also inherit some of the platform’s good reputation. Suitable for senders with under 50,000 emails/month.
Dedicated IP — you have your own IP address. Your reputation is 100% your own. Requires thorough warmup but gives full control. Suitable for senders with over 100,000 emails/month.
Most start on shared IP and switch to dedicated when volume justifies it.
Prerequisites for warmup
Before starting warmup, the foundation must be in place:
- SPF, DKIM, and DMARC correctly configured
- Consent management — only send to contacts who gave consent
- Clean list — verify all addresses before warmup to avoid high bounce rates
- Good content — emails that generate engagement (opens, clicks, replies) strengthen warmup
Signs that warmup is going wrong
- Bounce rate above 5% — stop and clean the list
- Spam complaint rate above 0.3% — reduce volume and check content
- Declining open rates — you may be sending to too many unengaged contacts too early
- Emails landing in the promotions tab — this is normal and not necessarily a problem, but replies from recipients help you reach the primary inbox
Patience is critical. Read more about the technical foundation in our email deliverability guide.