When you get a new dedicated IP from an ESP (SendGrid, Mailgun, Postmark, SES), it has zero reputation. Gmail, Outlook, and Yahoo have never seen it before. If you send 10,000 emails on day one, you'll get throttled or junked immediately.
Warmup is the process of slowly increasing send volume so ISPs build a positive reputation profile on your IP. There are no shortcuts.
| Day | Daily volume | What to expect |
|---|---|---|
| 1-3 | 50 | Send to your most engaged contacts only. Open rates should be 40%+. |
| 4-7 | 100-200 | Expand to recent openers. Some Gmail deferrals are normal. |
| 8-14 | 500-1,000 | Add regular subscribers. Monitor spam folder placement. |
| 15-21 | 2,000-5,000 | Full active list. Inbox rates should stabilize at 80%+. |
| 22-30 | 5,000-10,000 | Ramp to full volume. If inbox rate drops, slow down. |
| 30+ | Full volume | Warmup complete. Maintain consistent daily volume. |
Engagement signals. Open rates, click rates, replies. Gmail weighs engagement heavily. This is why you send to your most engaged contacts first — their interactions teach Gmail that mail from your IP is wanted.
Complaint rates. If more than 0.1% of recipients mark your email as spam, warmup is in trouble. Use confirmed opt-in lists only during warmup.
Consistent volume. ISPs are suspicious of volume spikes. Don't send 500 on Monday and 5,000 on Tuesday. Gradual, daily increases are key.
Authentication. SPF, DKIM, and DMARC must be correctly configured before you send the first email. Missing authentication during warmup poisons the reputation you're trying to build.
Here's what most warmup guides don't mention: your IP's /24 block affects warmup speed.
When Gmail evaluates your new IP, it looks at what it knows about the surrounding IPs. If your /24 is full of active senders with clean records, Gmail has a positive prior — your new IP gets the benefit of the doubt. If your /24 is empty (a "ghost block") or contains blacklisted IPs, Gmail starts with suspicion.
This is why the same warmup schedule produces different results for different IPs. The IP itself is identical in configuration — the difference is the neighborhood.
Before investing 4-6 weeks in warmup, spend 60 seconds scanning your IP's /24 block. If you're in a ghost block or a block with SBL listings, consider requesting a new IP from your ESP. Most ESPs will reassign you at no cost — you just have to ask.
It's cheaper to get a good IP before warmup than to discover your neighborhood is bad after 3 weeks of poor inbox rates.
Skipping warmup entirely. "We only send 500 emails/day, we don't need warmup." Yes you do. Any new IP needs warmup, regardless of volume.
Warming up with old lists. Sending to contacts who haven't opened in 6 months during warmup is self-sabotage. Low engagement teaches ISPs your email isn't wanted.
Stopping on weekends. ISPs expect consistent daily volume. Sending Mon-Fri and going silent Sat-Sun looks irregular. Send 7 days a week during warmup.
Panicking at deferrals. Gmail will defer (temporarily reject) some messages during early warmup. This is normal — it's Gmail throttling an unknown sender. Don't increase volume to compensate. Wait, retry, and stay on schedule.
See if your /24 is a gold block or a ghost town. Free, 60 seconds.