# IP warmup

> IP warmup is the gradual volume ramp that earns a new sending address its reputation with each mailbox provider, and what happens to senders who skip it.

Canonical: https://emailfast.dev/glossary/ip-warmup

IP warmup is the practice of ramping send volume gradually from a new IP address so that mailbox providers can build a history for it. Reputation systems treat an unknown IP that suddenly sends at scale as a compromised machine, because that is usually what it is.

## Why it matters

Skip warmup and providers respond in escalating order: deferrals (4xx "try again later" responses), spam-foldering, then blocklisting. A burned IP takes longer to rehabilitate than a fresh one takes to warm, so the shortcut costs more than the patience. Reputation is also kept *per provider*: Gmail, Microsoft, and Yahoo each score an IP separately, so a ramp Gmail accepts can still be too fast for Microsoft, and a schedule that ignores this warms one door while another closes.

## In practice

A warmup starts small, in the low hundreds of messages per day per provider, and grows on green signals: mail accepted promptly, no deferral clusters, no complaint spikes. On a bad signal the correct move is to hold or step back, not push through, because deferrals are the provider saying "slow down" politely before it stops being polite. Reaching steady bulk volume typically takes weeks, which is why warmup should begin before the day the capacity is needed, and why the sane version is automated rather than a spreadsheet and a calendar reminder.

## How Email Fast handles it

Email Fast's warmup engine is automated and health-gated: it ramps each IP per receiving-provider group on live delivery signals, and it backs off on deferrals instead of blasting through them. It works together with [dedicated IP](/glossary/dedicated-ip) pool management, and it arms with live sending at launch.