What Is Inbox Warmup and Why Does It Matter?
Before we send a single cold email on your behalf, your sending inboxes go through a 22–28 day warmup process. This is one of the most important and most often misunderstood parts of cold email infrastructure. Here's everything you need to know.
The Problem Warmup Solves
Email providers like Gmail and Outlook make trust decisions about every sender. A brand new email address that suddenly starts sending 50–100 emails per day looks like spam to their algorithms. The result: your emails land in spam, your sender reputation tanks, and your campaign is dead before it starts.
Warmup solves this by establishing a legitimate sending history before your campaign goes live. It's the difference between walking into a room where people already know you versus walking in cold and immediately pitching everyone.
How Warmup Works
Our warmup system runs automatically on every new inbox from day 1. Here's what happens under the hood:
Phase 1: Low Volume (Days 1–7)
The inbox sends 5–10 emails per day to other warmed accounts in our network. These emails are automatically opened, replied to, and occasionally moved from spam to inbox. All of these are positive engagement signals that tell email providers "this sender is legitimate."Phase 2: Ramp Up (Days 8–18)
Volume increases gradually: 15, 25, 35 emails per day. Open rates remain high. Reply rates remain high. Spam folder moves drop to zero. The inbox is building a track record.Phase 3: Stabilization (Days 18–28)
Volume approaches campaign-ready levels (40–50 per day). The inbox's reputation score stabilizes above 85%. At this point, email providers recognize it as a legitimate, active sender.Go-Live
Once all 12 of your inboxes hit 85%+ average reputation, your campaign activates automatically. You'll receive a notification.Reading Your Warmup Stats
In your Campaigns tab, look for the Warmup Status card. It shows:
Avg Reputation Score The average reputation across all your inboxes, expressed as a percentage. This is the key metric.
| Score | Meaning |
| --- | --- |
| 90–100% | Excellent: campaign-ready |
| 85–89% | Ready: at our launch threshold |
| 70–84% | Good progress: 5–10 days to go |
| Below 70% | Still building: early stages |
Est. Go-Live Based on current trajectory, the projected date your campaign will activate. This is an estimate. If a few inboxes are lagging, the date may shift slightly.
Why We Use 12 Inboxes
Sending volume is distributed across 12 separate inboxes for several reasons:
What Happens If You Skip Warmup
This is worth understanding clearly: skipping warmup is not a shortcut. It's a way to destroy the campaign before it starts.
Without warmup:
- First batch of 500 emails sends
- 15–30% land in spam immediately
- Bounce rate spikes to 8–12% (vs our <3% target)
- Gmail/Outlook throttle or block the sending domain
- Domain reputation damage takes 60–90 days to recover
- First batch hits primary inbox at 85–95% delivery rate
- Open rates immediately at 35–50%
- Bounce rate stays under 2%
- Domain reputation grows stronger with each send
- Emails appear to come directly from your company
- Your domain reputation is entirely yours, not shared with other clients
- If we ever stop working together, you own the warmed domain
With proper warmup:
The 22–28 day investment is not a delay. It's what makes the campaign work.
PIQ Pro: Custom Domain Warmup
On PIQ Pro, we register dedicated sending domains branded to your company (e.g., getacmecorp.com) and warm 12 exclusive inboxes on those domains. The warmup process is identical, but the result is:
Frequently Asked Questions
Can I speed up the warmup process? No, and attempting to would be counterproductive. The warmup schedule is calibrated for maximum reputation building without triggering spam filters. Sending more aggressively during warmup would damage, not accelerate, the process.
What if the go-live date passes and nothing happens? It means one or more inboxes haven't reached 85% yet. This can happen if email providers were slower to register positive signals. Your CSM will be monitoring and will contact you if warmup extends significantly past the estimate.
Will I be charged during warmup? No. Billing starts when your campaign goes live. See When Does Billing Start? for the full explanation.
Can my inboxes lose reputation after warmup? Yes, but only if sending practices deteriorate: high bounce rates, spam complaints, or sending to invalid addresses. Piqely monitors this in real time and adjusts sending if we detect reputation erosion.