Email Warmup: How to Warm Up a New Domain
A new sending domain starts with zero reputation, so providers assume the worst. Warmup builds trust on purpose: start small, send mail people open, and ramp volume slowly enough to stay out of spam.
A new sending domain has no history. The first time a mailbox provider sees mail from it, they have nothing to judge you on, so they assume the worst and watch closely. Warmup is the process of building that history on purpose: start tiny, send mail that people actually open, and grow volume slowly enough that providers learn to trust you before you ask them to handle real volume. Skip it and your first big send lands in spam, where it teaches the provider exactly the wrong lesson about you.
What email warmup actually does
Providers like Gmail and Microsoft 365 score senders on reputation, and reputation is tied to your domain (and to a lesser degree your sending IP). A brand new domain sits at zero. Warmup moves that score up by feeding the provider a steady, growing stream of mail that gets opened, replied to, and rarely marked as spam.
The signals that move reputation during warmup are simple:
- Consistency. Sending a little every day beats sending a lot once. Providers reward predictable patterns and distrust sudden spikes.
- Engagement. Opens and replies tell the provider real humans want your mail. This is why warmup should target your most engaged recipients first.
- Low complaints and low bounces. One spam complaint per thousand is a soft ceiling. A pile of bounces on a fresh domain reads as a list you did not clean, which looks like spam behaviour.
- Authentication. SPF, DKIM, and DMARC must pass before you send a single warmup email. They are not optional and they are not part of the ramp.
A sensible ramp schedule
There is no single official table, because providers do not publish their thresholds. The numbers below are a conservative starting point that has worked for cold and transactional senders alike. Treat them as a ceiling, not a target: if engagement dips or complaints climb, hold the current volume for a few more days before stepping up.
| Day range | Emails per day | Send to |
|---|---|---|
| Days 1 to 3 | 20 to 50 | Most engaged contacts only |
| Days 4 to 7 | 50 to 100 | Engaged contacts, multiple providers |
| Week 2 | 200 to 500 | Broaden to warm contacts |
| Week 3 | 1,000 to 2,000 | Wider warm segments |
| Week 4 | 3,000 to 5,000 | Approaching normal volume |
| Weeks 5 to 8 | Scale toward full volume | Full eligible list |
Two rules sit on top of the table. First, do not jump more than roughly double to triple your previous day. Second, spread sends across the day rather than firing everything at 9am, which looks more human and avoids tripping rate limits at the receiving end.
Domain warmup versus IP warmup
If you send through a shared pool (most ESPs), you are mainly warming the domain, because the IPs already carry reputation from other senders. If you have a dedicated IP, you warm both at once and the ramp matters more, since a cold IP plus a cold domain gives the provider two reasons to be cautious. The schedule above covers both; with a dedicated IP, lean toward the lower end of each range.
How to avoid landing in spam during warmup
Volume pacing is only half the job. The other half is making sure every warmup email is something a provider wants to deliver.
- Send to people who will open. Engagement is the strongest signal you control. Start with recent buyers, active users, or anyone who replied lately. Never warm up against a cold purchased list.
- Verify the list before you send. A fresh domain has zero margin for bounces. Clean the addresses first so you are not burning new reputation on dead mailboxes. Our free email verifier handles the first 100 free, and the wider habit is covered in email list hygiene.
- Authenticate fully. SPF, DKIM, and DMARC aligned and passing on day one. A DMARC policy of at least p=none with reporting tells you who is sending as you.
- Keep complaints under 0.1 percent. One complaint per thousand is the rough Gmail and Microsoft ceiling. Make unsubscribing obvious and honour it instantly.
- Watch catch-all domains. A catch-all accepts everything at SMTP time, so a bounce-free send can still be hitting dead addresses. See catch-all emails for why these inflate your apparent deliverability.
- Send real content, not test junk. Provider filters read content. Warm up with the kind of mail you actually intend to send, with real links and a real reply-to.
What to monitor while you ramp
- Bounce rate. Above 2 percent means pause and clean. This ties directly to reducing your bounce rate.
- Spam complaint rate. Above 0.1 percent means slow down and check who you are sending to.
- Open rate by provider. If Gmail opens look fine but Microsoft 365 drops, you have a placement problem at one provider, not a list problem.
- Google Postmaster Tools. Free, and the only direct window into how Gmail sees your domain reputation.
If any of those go red, the fix is almost never to push harder. Hold or step back, clean the list, and resume the ramp once the numbers settle. For the bigger picture beyond warmup, the deliverability guide and the complete guide to email verification go deeper.
FAQ
How long does email warmup take?
Plan for four to eight weeks to reach full volume on a brand new domain. Transactional senders with small, highly engaged lists can move faster; cold outreach senders should go slower. There is no shortcut that skips the calendar, because reputation is built from history and history takes days to accrue.
Can I warm up a domain and IP at the same time?
Yes, and you usually have to if you are on a dedicated IP. Warming both at once just means the provider is judging two cold things, so keep the early volume low and watch your metrics more closely. On a shared IP pool the IP is already warm, so you are mainly warming the domain.
Do warmup tools that auto-send and auto-reply work?
They can lift early engagement numbers, but they game a signal rather than earn it. Providers are getting better at spotting seed networks that only mail each other. They are a supplement at best. Real engagement from real recipients on a verified list is what actually moves reputation.