IP warming: how to build reputation on a new address
IP warming is the practice of sending small email volumes from a new or dormant IP address, then gradually increasing that volume over 2–6 weeks until you reach your normal sending rate. Mailbox providers track how recipients respond to mail from each IP. An unknown IP sending 100,000 messages on day one looks like a spam blast, because that is exactly what spam blasts look like.
Typical warming schedule
The standard approach doubles daily volume every two to three days. Example for a target of 100,000 per day: Day 1–2: 500. Day 3–4: 1,000. Day 5–6: 2,000. Day 7–8: 5,000. Day 9–10: 10,000. Day 11–12: 25,000. Day 13–14: 50,000. Day 15+: 100,000. Real timelines vary with list quality and how your subscriber base is distributed across providers. If 70% of your list is on Gmail, calibrate the pace against Gmail's own limits specifically.
Who to send to first
During warming, audience quality matters more than anything else. First messages should go to your most engaged subscribers: people who opened or clicked something in the last 30 days. Their positive responses give providers a reason to trust the new address. Sending to cold or unverified contacts at this stage can push bounce rate above 2% before you have built any goodwill. That is a hard position to recover from.
What to watch
Bounce rate should stay below 2%. If it climbs higher, stop and clean the list before continuing. Complaint rate should stay below 0.1%. SMTP response codes: a 421 (temporary reject) or 452 (too many connections) means you have exceeded the provider's pace limit. Hold volume for 2–3 days before increasing again. Open rate should run above your usual average, since you are sending to your best segment.
Common mistakes
Ramping every day instead of every two to three. Using an unverified list. Taking days off — gaps slow reputation formation because providers see inconsistent volume as suspicious. Treating the schedule as fixed: if bounce rate spikes to 5% on day three, pausing to investigate is the right call, not moving to the next step anyway.
uChecker is a necessary step before you start warming. Verify your list first: the service removes invalid addresses, spam traps, and risky contacts that would otherwise damage your reputation before it has a chance to form.
A workable schedule
Start at a few hundred messages on day one and roughly double every second day, holding steady whenever bounces or complaints tick up. Reaching a hundred thousand a day takes about four to six weeks; there is no way to compress it, because providers are watching consistency rather than totals.
Send to your most engaged recipients first. Opens and clicks in the opening days are what build the initial trust, so a warm-up aimed at a cold segment does the opposite of what it is for.
What resets the work
A pause is the usual culprit. Stop for a month and the reputation you built decays; resuming at full volume reads to a provider as a hijacked address. Steady weekly sending at modest volume beats occasional large campaigns.
The other reset is a dirty list. Warming an IP while mailing unverified addresses trains providers on your bounce rate instead of your engagement — the exact opposite of the intent.