Warm up your list (and your domain)
When you send an email, Gmail and Outlook don't really see you—they see your sending domain, and they judge it the way a small town judges a newcomer: by reputation. A brand-new domain has none. So if the first thing it ever does is send five thousand emails in an hour, it looks exactly like every spammer they've ever met—and the filters treat it that way. A domain that gets flagged in week one can spend months digging out.
The trap after a platform move
Your readers might know you and love you—but the inbox providers don't know your new domain. Your list can be warm while your domain is stone cold. That's exactly the situation after moving platforms or setting up a new sending domain: warm up even if you've been emailing this same list for years somewhere else.
The ramp
Warming up means building reputation the way trust is actually built: gradually.
- Week one: send only to your most engaged readers—the ones who open everything. Build a segment of recent openers or clickers and start there. Every open, click, and reply tells the providers your mail is wanted.
- Grow volume week over week—roughly doubling is a safe pace. Don't go from zero to your full list in one day.
- Spread each send over a few hours while the domain is young—the Delivery speed control does this for you (see the related guide).
- Watch the first sends closely. Open the campaign report after each one: a burst of bounces or a spam complaint in week one hurts far more than the same event on a warmed domain would.
The schedule
Find your list size and follow the sends left to right—each send goes to your most engaged readers first, adding the next-most-engaged slice each time, until the last send reaches your full list. Space sends 2–3 days apart; consistency builds reputation faster than speed does.
| List size | Send-by-send volumes | Takes about |
|---|---|---|
| 1,000 | 250 → 500 → 1,000 | 1 week |
| 2,500 | 250 → 500 → 1,000 → 2,500 | 10 days |
| 5,000 | 500 → 1,000 → 2,500 → 5,000 | 2 weeks |
| 10,000 | 500 → 1,000 → 2,500 → 5,000 → 10,000 | 2½ weeks |
| 25,000 | 500 → 1,000 → 2,500 → 5,000 → 10,000 → 20,000 → 25,000 | 3 weeks |
| 50,000 | 1,000 → 2,500 → 5,000 → 10,000 → 20,000 → 40,000 → 50,000 | 3½ weeks |
| 100,000 | 1,000 → 2,500 → 5,000 → 10,000 → 20,000 → 40,000 → 75,000 → 100,000 | 4–5 weeks |
Reading the chart:
- Between sizes? Use the next row up—a 15,000 list follows the 25,000 schedule and simply stops when it reaches everyone.
- Brand-new domain that has never sent mail? Halve the first send and add roughly a week. A platform move with an established domain follows the chart as-is.
- Check the campaign report before each doubling. If bounces rise above 2%, spam complaints above 0.1%, or opens suddenly drop—hold at the same volume for one extra send, then resume. (Those are the same thresholds the sending machinery itself enforces.)
When are you warm?
After a few weeks of clean history—steady sends, healthy opens, no complaint flags on your reports—your domain has a track record, and normal sending (your whole list, all at once) is fine.