When you start sending emails from a brand new IP address, inbox providers know nothing about you. You have no sending history, no reputation — you're a blank slate. And inbox providers treat unknown senders with suspicion.
IP warmup is the process of gradually increasing your sending volume over time to build a positive reputation with ISPs (Internet Service Providers) like Gmail, Yahoo, and Microsoft.
Why You Can't Just Start Sending
If you send 10,000 emails on day one from a new IP, most ISPs will flag your traffic as suspicious. You'll see high bounce rates, spam folder placement, or outright blocks. The damage to your IP reputation can take weeks to recover from.
Warmup prevents this by showing ISPs a consistent, growing pattern of legitimate email traffic with healthy engagement signals.
A Proven 30-Day Warmup Schedule
Here's a conservative warmup schedule that works for most senders:
| Day | Daily Volume |
|---|---|
| 1–2 | 200 |
| 3–4 | 500 |
| 5–7 | 1,000 |
| 8–10 | 2,500 |
| 11–14 | 5,000 |
| 15–20 | 10,000 |
| 21–25 | 20,000 |
| 26–30 | 40,000+ |
The key principle: double your volume roughly every 3–5 days, only if engagement metrics remain healthy.
Signals to Watch During Warmup
- Bounce rate: Should stay under 2%. Hard bounces above 5% mean your list needs cleaning.
- Spam complaints: Keep below 0.1%. If you're seeing higher rates, slow down.
- Open rates: Healthy open rates (15%+) during warmup signal good engagement to ISPs.
- Deferrals: Some temporary blocks are normal during warmup. They resolve as your reputation builds.
Tips for Successful Warmup
- Start with your most engaged subscribers. Send to people who regularly open and click your emails. Their positive engagement accelerates reputation building.
- Clean your list first. Remove bounced addresses, inactive contacts, and any addresses that haven't engaged in 6+ months before starting warmup.
- Be consistent. Send every day during the warmup period. Gaps in sending can reset your progress.
- Authenticate your domain. SPF, DKIM, and DMARC should all be configured before you send your first warmup email.
How NexSent Handles Warmup
NexSent includes built-in IP warmup management. Our system enforces daily sending limits per IP address following a warmup schedule, automatically distributes traffic across your IP pool, and handles provider-specific throttling for Gmail, Yahoo, and Outlook. You focus on your content — we handle the infrastructure.