A new IP address is like a new driver - it has no history, no reputation, and ISPs are naturally suspicious. Proper IP warmup is the process of building trust with mailbox providers, and getting it right is crucial for long-term deliverability success.
Why IP Warmup Matters
When you start sending from a new IP address, Internet Service Providers (ISPs) have no data to evaluate your legitimacy. Without an established sending history, they apply extra scrutiny to your emails, often throttling delivery or directing messages to spam folders.
IP warmup gradually introduces your sending patterns to ISPs, allowing them to build a positive reputation profile for your IP. Rush this process, and you risk permanent reputation damage that can take months to recover from.
The Golden Rules of IP Warmup
Before diving into specific strategies, understand these fundamental principles:
- Start small: Begin with your most engaged subscribers who are most likely to open and interact
- Increase gradually: Double your volume every 2-3 days, never more
- Monitor constantly: Watch bounce rates, complaints, and engagement metrics daily
- Stay consistent: Send at the same time each day during warmup
- Pause if needed: If metrics decline, reduce volume and stabilize before continuing
Sample Warmup Schedule
Here's a proven 30-day warmup schedule for reaching 100,000 daily sends:
- Days 1-2: 500 emails/day to your most engaged subscribers
- Days 3-4: 1,000 emails/day
- Days 5-6: 2,500 emails/day
- Days 7-8: 5,000 emails/day
- Days 9-10: 10,000 emails/day
- Days 11-14: 25,000 emails/day
- Days 15-21: 50,000 emails/day
- Days 22-30: 75,000-100,000 emails/day
Segmentation Strategy During Warmup
The order in which you add subscribers matters enormously. Structure your warmup cohorts like this:
- Week 1: Subscribers who opened an email in the last 30 days
- Week 2: Subscribers who opened in the last 60 days
- Week 3: Subscribers who opened in the last 90 days
- Week 4: Remaining active subscribers (opened in last 6 months)
Never include subscribers who haven't engaged in over 6 months during warmup - these addresses are high-risk and can torpedo your reputation before it's established.
Key Metrics to Monitor
During warmup, track these metrics obsessively:
- Bounce rate: Should stay below 2%. Above 5% is a red flag.
- Complaint rate: Must stay below 0.1%. Above 0.3% requires immediate action.
- Open rate: Should be higher than your historical average due to engaged segments.
- Delivery rate: Target 98%+ for major ISPs.
Common Warmup Mistakes
Avoid these pitfalls that derail many warmup efforts:
- Sending to purchased or rented lists
- Including old or unengaged subscribers too early
- Ramping volume too quickly after good initial results
- Changing content or sending patterns mid-warmup
- Ignoring warning signs in metrics
Automated Warmup with SMTPCloud
Managing IP warmup manually is time-consuming and error-prone. SMTPCloud's automated warmup system handles the entire process, dynamically adjusting send volumes based on real-time reputation signals and ISP feedback.
Our system monitors deliverability metrics across all major ISPs and automatically throttles or increases volume to optimize reputation building while protecting against sudden reputation damage.