How to warm up an email domain (the 21-day ramp that works)
Warm up by sending small, growing volumes of real, engaged email over ~21 days on a sigmoid curve — not a linear ramp. Here's the exact schedule and the mistakes that get you flagged.
Short answer: to warm up a new email domain, send a small, steadily-growing volume of genuine, replied-to email over roughly 21 days following a sigmoid (S-curve) ramp — slow start, steep middle, gentle plateau. A linear ramp trips Gmail's behavioural classifier; organic growth mimics a real human inbox.
Why 21 days and why sigmoid
Mailbox providers score sending *reputation* on how human your pattern looks. A brand-new domain that jumps to 200 sends/day on day one looks like a spammer. The sigmoid ramp starts at ~10–20/day, accelerates through week two, and plateaus — exactly how a real person's outreach grows.
The schedule
- Days 1–5: 10 → 30/day, only to engaged recipients, ask for replies.
- Days 6–14: 30 → 120/day, mix in your real list slowly.
- Days 15–21: 120 → your target cap, watch the spam-rate gauge.
The three mistakes
- Skipping authentication. No SPF/DKIM/DMARC = no warmup will save you. Set DMARC to at least p=quarantine.
- Linear ramps. They're predictable; classifiers flag predictable.
- No reply loop. Replies are the strongest positive signal. Seed real conversations.
Autocloz runs a 21-day sigmoid warmup on every new mailbox automatically and seed-tests inbox placement weekly — so you don't babysit it.
> Start free and connect a mailbox — warmup begins the moment it's added.