IP Warmup Guide: Schedule & Best Practices
A brand-new IP has no reputation, and mailbox providers distrust strangers. IP warmup is the process of slowly building trust by ramping volume. Here's a proven schedule.
TL;DR
Warm up by ramping volume gradually over 4–8 weeks, sending to your most engaged contacts first, and watching bounces and complaints. AutoPMTA automates warmup curves per VMTA.
Why warmup is mandatory
When a new IP suddenly sends 100,000 emails, providers read it as a spam attack and throttle or block you. Warmup signals "this is a real, careful sender." Skip it and you'll land in spam — sometimes permanently.
A sample warmup schedule
| Day | Daily volume | Focus |
|---|---|---|
| 1–2 | 50–100 | Most engaged contacts only |
| 3–5 | 500 | Openers from last 30 days |
| 6–10 | 1,000–5,000 | Active subscribers |
| 11–20 | 10,000–50,000 | Broaden gradually |
| 21–40 | 100,000+ | Full list, monitor closely |
These are starting points — adjust to your list size and engagement. High-volume senders may take 8 weeks to reach full capacity.
Warmup best practices
- Send to engaged contacts first. Opens and clicks build positive reputation fast.
- Ramp consistently. Sudden spikes look like spam; steady growth looks human.
- Keep volume per ISP balanced. Don't dump everything on Gmail at once — PowerMTA's per-domain throttling helps here.
- Authenticate first. Warmup is pointless without SPF, DKIM and DMARC in place.
What to monitor
- Bounce rate (keep under ~2–3%).
- Spam complaints (keep under 0.1%).
- Blacklist status on your IPs.
- Inbox placement at Gmail, Outlook, Yahoo.
Our deliverability guide expands on each metric.
Dedicated vs shared during warmup
Warmup only applies to dedicated IPs — on a shared pool you inherit others' reputation. See dedicated vs shared IPs to choose.
AutoPMTA automates IP warmup with per-VMTA ramp curves and live reputation monitoring. See plans.
Key takeaways
- Ramp new IP volume gradually over 4–8 weeks.
- Start with your most engaged contacts.
- Authenticate before you warm up — SPF/DKIM/DMARC first.
- Watch bounces, complaints and blacklist status throughout.