Email IP Warm-Up Guide: How to Build Sender Reputation on a New IP
Starting fresh with a new IP address or domain? Here's how to warm it up properly — with a week-by-week schedule and the mistakes that kill deliverability before it starts.
Why IP warm-up matters
A new IP address has no sending history, which means mailbox providers treat it with suspicion. If you start blasting thousands of emails from a cold IP, Gmail and Outlook will assume you're a spammer and start filtering or blocking your messages.
IP warm-up is the process of gradually increasing your sending volume over weeks to build a positive reputation. The goal is to establish a track record of high engagement and low complaints before sending at full volume.
Warm-up schedule
These are guidelines, not rules. Pause and investigate if bounce rates exceed 2% or complaint rates exceed 0.1% at any stage before increasing volume.
IP warm-up weekly volume schedule
| Week ↕ | Max Daily Volume ↕ | Audience Segment ↕ | Key Metric to Watch ↕ |
|---|---|---|---|
| Week 1 | 50–100 | Most engaged: opened in last 30 days | Bounce rate < 1% |
| Week 2 | 200–500 | Highly engaged: opened in last 45 days | Complaint rate < 0.05% |
| Week 3 | 1,000–2,000 | Engaged: opened in last 60 days | Domain reputation: Good |
| Week 4 | 5,000–10,000 | Recent subscribers: within 90 days | Inbox placement > 90% |
| Week 5 | 25,000–50,000 | Active list segments | Postmaster Tools: Good or High |
| Week 6+ | 100,000+ | Full list (exclude unengaged) | All metrics stable for 2+ weeks |
When to pause warm-up
If bounce rates exceed 2%, complaint rates exceed 0.1%, or Google Postmaster Tools drops below Medium reputation, stop increasing volume. Diagnose and fix before continuing.
What to monitor during warm-up
Google Postmaster Tools: Register your domain and monitor domain reputation (Good/Medium/Low/Bad) and IP reputation. Reputation should stay at Good or Medium.
Microsoft SNDS: Register your sending IPs at Microsoft's Smart Network Data Services for Outlook/Hotmail reputation data.
Bounce rates: Should stay under 2%. Spikes indicate list quality issues.
Spam complaint rates: Must stay under 0.1% (Gmail) and 0.08% (Yahoo).
Blacklist status: Check daily during warm-up. Getting listed during warm-up is common and must be addressed immediately.
Warm-up best practices
Only send to confirmed opt-in addresses during warm-up — this is not the time to scrub old lists.
Use consistent sending times and patterns — erratic sending looks spammy.
Ensure SPF, DKIM, and DMARC are fully configured before sending the first email.
If using a dedicated IP with an ESP, ask if they offer an automated warm-up tool — most major providers (SendGrid, Mailgun, Postmark) do.
For domain warm-up (new domain, not just new IP), the process is similar but focus on domain reputation in Postmaster Tools.
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