What is IP warming?
IP warming (also called IP warm-up) is the process of gradually increasing email volume from a new or cold dedicated IP address. Mailbox providers treat sudden high volume from an unknown IP as suspicious — similar to botnet behavior. Warming builds a positive sending reputation so your emails reach the inbox instead of being throttled or sent to spam.
A well-executed warm-up typically takes 30–45 days and focuses on consistent, engaged sending patterns.
When do you need to warm an IP?
- You are moving to a new dedicated IP address
- You added a fresh IP to your existing pool
- You switched email service providers and received new IPs
- An existing IP has been idle for 30+ days
- You recovered an IP after a blocklist incident
If your sending domain is also new, run domain warming in parallel.
Prerequisites before starting
- Complete SPF, DKIM, and DMARC setup with proper alignment (see the email authentication guide).
- Set up a valid reverse DNS (PTR) record for the IP.
- Publish a DMARC record with a
ruareporting address. - Use a dedicated sending subdomain (e.g.
news.example.comortx.example.com) instead of your root domain. - Prepare your most engaged subscriber segment (recent openers and clickers) for the first days.
30-day IP Warm-up Schedule
This is a conservative ramp that doubles volume gradually. Adjust based on your list size and engagement.
| Day | Daily Volume | Target Audience |
|---|---|---|
| 1–2 | 1,000 | Top engaged (last 7 days) |
| 3–4 | 2,000 | Top engaged |
| 5–6 | 4,000 | Top 5% engaged (last 30 days) |
| 7–8 | 8,000 | Top 5% engaged |
| 9–10 | 16,000 | Top 10% engaged |
| 11–14 | 30,000 – 60,000 | Top 20% engaged |
| 15–18 | 120,000 | Last 90-day engaged |
| 19–22 | 250,000 | Last 180-day engaged |
| 23–26 | 500,000 | Active list |
| 27–30 | 1,000,000+ | Full active list |
Send throughout the day instead of in bursts. Consider throttling per provider (Gmail, Yahoo, Outlook) if your sending system supports it.
IP Warming Best Practices
- Start with your highest-engagement recipients
- Send every day — consistency matters more than volume
- Immediately suppress hard bounces
- Avoid heavy promotions in the first 1–2 weeks
- Balance volume across major providers
- Combine with domain warming when using a new from-domain
What to Monitor Daily
- Bounce rate — keep under 2%
- Complaint rate — target under 0.1% (max 0.3%)
- Open rates — watch for sudden drops
- Gmail Postmaster Tools — IP & domain reputation
- DMARC reports — authentication pass rate
- Blocklist status (Spamhaus, etc.)
Troubleshooting a Stalled Warm-up
- Slow down immediately — reduce volume by 50% the next day
- Re-focus on your most engaged segment for a few days
- Double-check SPF, DKIM, and DMARC alignment
- Verify the IP is not on any blocklists
- Look for sudden spikes in soft bounces or complaints
Successful IP warming relies on patience, consistent sending, and strong list hygiene. Combine it with proper authentication, domain warming, and good email practices for the best results.