Deliverability & the inbox
IP warming
Also known as: IP warm-up · sender warming
Gradually ramping email volume from a new or dedicated IP over 2-6 weeks to build sender reputation — mailbox providers watch early volume and engagement signals to decide whether the IP is legitimate.
IP warming is the controlled ramp-up of email volume from a new, unused, or newly-dedicated IP address. Mailbox providers (Gmail, Outlook, Yahoo) maintain per-IP reputation scores. A brand-new IP has zero history — sending high volume immediately triggers rate-limiting, throttling, or outright blocks. The warm-up schedule starts small (hundreds per day), ramps exponentially over 2-6 weeks, and targets the most-engaged segments first to build positive engagement signals. A typical ramp: day 1, 500 sends; day 3, 1,500; day 7, 5,000; day 14, 25,000; day 28, full volume. Most ESPs offer IP warming as a managed service but the operator still needs to coordinate: send only the most engaged audience first, watch bounce and complaint rates daily, pause ramp if either spikes. Getting warm-up wrong can damage reputation for weeks.
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