What Is Email Warm-Up? A Complete IP Warming Guide
What Is Email Warm-Up? A Complete IP Warming Guide
If you have ever launched a new email marketing program or switched to a new sending domain and seen your emails land in spam, a missing or rushed warm-up is likely the cause.
This guide explains exactly what email warm-up is, why it matters, and how to execute it correctly.
What Is Email Warm-Up?
Email warm-up is the process of gradually increasing the volume of emails sent from a new IP address or domain over several weeks. The goal is to build a positive sending reputation with Internet Service Providers (ISPs) like Gmail, Outlook, and Yahoo before sending at full scale.
ISPs monitor new sending sources closely. A brand-new IP that suddenly sends 100,000 emails in a day is a classic spammer pattern. By starting small and increasing volume predictably, you prove to ISPs that you are a legitimate sender.
Why Is Warm-Up Necessary?
Every IP address has a sender reputation — a score based on:
- Volume and consistency of sending
- Bounce rates
- Spam complaint rates
- Engagement rates (opens, clicks, replies)
- Blacklist status
A new IP has zero reputation history. ISPs cannot distinguish it from a spammer's freshly provisioned IP. Warm-up gives your IP time to accumulate positive engagement signals.
Without warm-up, even a legitimate sender with a clean list can see:
- 30–60% of emails landing in spam
- Temporary blocks from Gmail, Outlook, or Yahoo
- Permanent IP blacklisting in severe cases
IP Warm-Up Schedule
Here is a standard warm-up schedule for a new IP:
| Week | Daily Volume |
|---|---|
| Week 1 | 50–200 |
| Week 2 | 500–1,000 |
| Week 3 | 2,000–5,000 |
| Week 4 | 10,000–20,000 |
| Week 5 | 40,000–50,000 |
| Week 6 | 100,000+ |
For high-volume programs (1M+ emails/month), extend the warm-up to 8–10 weeks.
Domain Warm-Up
A new sending domain also needs to be warmed up, even if you are using a shared IP pool. Domain reputation is increasingly important — Gmail and Outlook both score domains independently of IP reputation.
For domain warm-up:
- Start sending small volumes from the new domain
- Use the domain only for legitimate opt-in email
- Set up SPF, DKIM, and DMARC before the first send
- Monitor Google Postmaster Tools for domain reputation signals
What to Send During Warm-Up
Send to your best subscribers first. During warm-up, every open, click, and reply matters. High engagement builds reputation fast.
Prioritize:
- Recent opt-ins (subscribed within 30 days)
- Loyal customers who frequently open
- Transactional email recipients (they expect your email)
Avoid during warm-up:
- Inactive subscribers (no opens in 90+ days)
- Purchased or scraped lists (never, but especially not during warm-up)
- Large promotional blasts
Warm-Up for Shared vs. Dedicated IPs
Shared IP pool: Your reputation is influenced by all senders on the pool. Reputable platforms manage pool reputation on your behalf, but your sending behavior still matters.
Dedicated IP: You own the entire reputation. Full control, full responsibility. Required for senders above ~100,000 emails/month who need predictable deliverability.
MisarMail offers both shared and dedicated IP options with built-in warm-up scheduling.
Signs Your Warm-Up Is Going Well
- Spam rate below 0.1% (check Google Postmaster Tools)
- Bounce rate below 2%
- Inbox placement above 90%
- No blacklist listings
- Open rates consistent with your historical benchmarks
Signs Your Warm-Up Is Struggling
- Spam folder placement above 10%
- Soft bounce rate spiking
- Complaints above 0.3%
- Gmail or Outlook deferrals in bounce logs
If warm-up is struggling, reduce volume immediately and re-engage your cleanest subscribers before trying to scale again.
See also: How to Improve Email Deliverability