A dedicated IP is only an advantage if mailbox providers already trust it. A brand-new address has no reputation. Treat the first two to four weeks as a controlled introduction, not a launch party.
Why warmup exists
Gmail, Microsoft, and Yahoo watch volume, complaint rate, unknown-user rate, and whether engaged humans open the mail. A cold IP that suddenly sends tens of thousands of messages looks like a compromised host. Warmup is how you prove you are a real sender before you ask for inbox placement at scale.
A conservative schedule
- Days 1–3: a few hundred messages per day to your most engaged subscribers only.
- Days 4–7: double volume only if bounce rate stays under 2% and complaints stay well under 0.1%.
- Week 2: add slightly older but still opted-in names. Do not dump the full list.
- Week 3–4: step toward production volume. Pause and investigate if complaints or blocks appear.
Who should receive warmup mail
Send to people who recently opened or clicked. Skip role accounts, purchased lists, and addresses that have not engaged in months. Those cohorts create spam-trap and complaint risk exactly when the IP is most fragile.
Authentication and infrastructure
SPF, DKIM, and DMARC should already pass before the first warmup message. Align the From domain with DKIM. Keep a consistent HELO/EHLO name. If you also send from a shared pool, do not mix the new dedicated IP into the same campaign until warmup is done.
When to stop or slow down
If you see 421/450 deferrals, junk-folder placement on seed tests, or a spike in 550 user-unknown, cut volume in half for 48 hours and clean the list. Warmup is not a substitute for list hygiene. It only works if the mail itself is wanted.
