skipping warmup is the #3 reason campaigns fail (after DNS misconfiguration and single-provider setups).
a new inbox with zero sending history that suddenly sends 100+ cold emails on day one gets flagged immediately. email providers assume it's spam because real business accounts don't behave that way.
warmup builds your sender reputation gradually. you send emails that get opened and replied to, proving to Google and Outlook that you're a legitimate sender.
this is the schedule we use at Premium Inboxes for every deployment. adjust volumes based on your total sending targets, but the timeline stays the same.
week 1: foundation (days 1-7)
| Day | Warmup Emails/Day | Cold Sends/Day | Total |
|---|---|---|---|
| 1-3 | 10-15 | 0 | 10-15 |
| 4-5 | 15-20 | 0 | 15-20 |
| 6-7 | 20-25 | 0 | 20-25 |
zero cold sends. warmup only. the inbox is building a positive engagement history from scratch.
week 2: introduction (days 8-14)
| Day | Warmup Emails/Day | Cold Sends/Day | Total |
|---|---|---|---|
| 8-10 | 20-25 | 5-10 | 25-35 |
| 11-12 | 20-25 | 10-15 | 30-40 |
| 13-14 | 20-25 | 15-20 | 35-45 |
you start introducing cold sends at low volumes. warmup continues alongside. the ratio matters because positive warmup engagement offsets the lower engagement you'll see on cold sends.
week 3: scaling (days 15-21)
| Day | Warmup Emails/Day | Cold Sends/Day | Total |
|---|---|---|---|
| 15-17 | 15-20 | 20-30 | 35-50 |
| 18-19 | 15-20 | 30-40 | 45-60 |
| 20-21 | 10-15 | 40-50 | 50-65 |
warmup volume decreases as cold volume increases. by day 21, your inbox has 3 weeks of positive sending history behind it.
after day 21:
keep warmup running at 10-15 emails per day indefinitely. some teams turn off warmup after launch, which is a mistake. that ongoing positive engagement is a safety net for your sender reputation.
monitor these metrics daily during the 21-day period: