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: warm a new domain by sending a small, steadily-growing volume of genuine, replied-to email over roughly 21 days on a sigmoid (S-curve) ramp — slow start, steep middle, gentle plateau. A linear ramp trips Gmail's behavioural classifier. An S-curve reads like a real inbox growing.
Why 21 days and why sigmoid
Mailbox providers score *reputation* on how human your pattern looks. A brand-new domain that hits 200 sends on day one screams spammer. The sigmoid ramp opens at ~10–20/day, accelerates through week two, then plateaus — the same shape a real person's outreach traces as it 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 and no warmup can save you. Set DMARC to at least p=quarantine first.
- Linear ramps. They're too regular. Classifiers flag regular.
- No reply loop. Replies are the strongest positive signal there is. Seed real conversations, not silence.
Autocloz runs a 21-day sigmoid warmup on every new mailbox automatically and seed-tests inbox placement every week, so you're not the one babysitting it.
> Start free and connect a mailbox — warmup kicks off the moment it's added.