IntermediateReputation · 7 min read

IP warming, the slow build

A new dedicated IP has zero reputation. Send full-volume on day one and you go to spam for weeks. Here is the curve we use.

Receiving ISPs maintain a per-IP reputation score. A brand-new IP has no history, which most receivers treat as suspicious. Send 200,000 emails on day one and you will be parked in the spam folder for a month.

The warming curve

A standard curve doubles volume every 36 hours, starting at 50 sends on day one. Across six weeks you reach production volume.

plainDay 1:    50 sends
Day 3:   100
Day 5:   200
Day 7:   400
Day 9:   800
Day 11: 1,600
Day 13: 3,200
…
Day 36: 100k
Day 42: 400k+ (production)

Send to your most-engaged audience first

During warm-up, only send to recipients who have opened mail in the last 30 days. They are guaranteed to engage, which produces a positive reputation signal. Save your cold list for after the warm completes.

Watch the metrics

Bounce rate >2% — slow the curve, do not double the next day.
Complaint rate >0.05% — pause for a day, investigate the cohort.
Open rate <15% — your list is colder than you think; trim it.

Skipping the warm because "we are urgent" is the most expensive shortcut in email. A botched warm parks an IP in spam for 6-8 weeks; a clean warm parks it in the inbox forever.

Re-warming

If you stop sending for more than 30 days from a dedicated IP, you need to re-warm — though faster than the initial curve. We auto-detect dormancy and propose a 14-day re-warm.

In VoltMail: dedicated IPs on Pro Max are auto-warmed. We pace the curve, route to your most-engaged segments, and pause if any metric drifts off plan. You see a daily progress chart.