A fresh domain has no reputation. None. To inbox providers, a new domain pushing ten thousand messages on day one is indistinguishable from a spam operation. Warmup is the ritual that tells providers this is a real sender, slowly, with the engagement evidence they expect to see before they trust you with volume.
Why warmup exists
Inbox providers model senders over time. A new domain with sudden volume hits the same statistical filter that catches bulk spammers. They cannot tell you apart from a throwaway in the first forty-eight hours. The only thing that distinguishes you is the pattern of engagement your audience produces in response to the volume you send.
Warmup is the deliberate production of that pattern. Send small. Send to people who will engage. Grow volume slowly. Each day of clean engagement raises the cap on what you can send the next day without tripping the filter.
Any domain intending to send more than a few hundred messages a day needs it. Even purely transactional senders need it when volume is material. The only senders who can skip warmup are low-volume personal or internal mail.
A schedule that works in two weeks
Begin with thirty to fifty messages on day one. Target your most engaged segment: subscribers who have opened something in the last thirty days, or internal accounts you can guarantee will open. Roughly double volume every second day, watching the signals in the next section after each step.
A workable ramp
- Days 1 to 2. 30 to 50 per day.
- Days 3 to 4. 100 to 150 per day.
- Days 5 to 6. 300 to 500 per day.
- Days 7 to 8. 1,000 to 2,000 per day.
- Days 9 to 10. 3,000 to 5,000 per day.
- Days 11 to 12. 8,000 to 12,000 per day.
- Days 13 to 14. Target daily volume.
Segment by mailbox provider during warmup. Gmail, Outlook, Yahoo, and Apple each track your domain independently. Each needs its own evidence of engagement before it will route volume to the inbox. Sending ninety percent of day-one volume to Gmail and none to Outlook leaves Outlook cold when you need it.
Mix in reply-generating sends if you have them. A reply is the single strongest engagement signal a mailbox provider can see.
Signals to watch every morning
Three numbers matter during warmup:
- Bounce rate. Target under one percent. Above two percent, stop ramping and investigate the list source.
- Complaint rate. Target under 0.1 percent. Above 0.3 percent, stop ramping entirely and tighten the audience.
- Open rate. At least twenty percent for the warmup cohort. If openers are dropping below that, you are sending to the wrong people for this phase.
Google Postmaster Tools and Microsoft SNDS show you what each provider thinks of your domain, day by day. Check them every morning during warmup. They are the fastest and most authoritative feedback loop you get.
If any number breaks, hold volume for forty-eight hours. Do not double down. Doubling down is how domains go cold on day five.Postelist field notes
When you are warm enough to scale
After fourteen days of clean signals at your target daily volume, the domain has real reputation at each of the major mailbox providers. The reputation is now yours to maintain, not to build.
Maintenance is simpler than warmup, but not effortless. Keep sending to engaged recipients. Keep the list clean. Watch complaint rate on every campaign. The fastest way to burn a freshly warmed domain is to reach for a dormant segment three weeks in, chasing conversions the engaged segment will not produce.
A week of no sends is fine. Three weeks of silence requires a short re-warmup before returning to full volume. Reputation decays faster than it builds.