Inbox warmup is one of those things everyone knows they should do and almost nobody does correctly. The typical mistake: connecting a new inbox, enabling warmup, and then starting campaigns two weeks later because it "feels like enough time."
It isn't. Here's the actual protocol — the day-by-day schedule we use, and the specific metrics that tell you when you're ready.
Why warmup takes 30 days (not 14)
A fresh domain has zero sender reputation. Gmail and Outlook maintain reputation scores at both the domain and IP level — and these scores update slowly. Positive engagement signals (opens, replies, moves out of spam) accumulate gradually, not overnight.
Two weeks of warmup is enough to avoid the most obvious spam triggers. Thirty days is enough to build the kind of reputation that sustains a consistent campaign at 50+ emails/day without deliverability issues.
The 30-day schedule
Days 1–7: Foundation (5–15 emails/day)
Keep volume very low. Focus entirely on quality engagement — every warmup email sent and received should be opened, read, and replied to. This phase is about signalling to inbox providers that this is a legitimate, active mailbox.
Target metrics: 60%+ open rate on warmup emails, 30%+ reply rate. If you're below these, your warmup network isn't generating enough engagement.
Days 8–14: Building (15–30 emails/day)
Gradually increase volume. By day 14 you should have a visible reputation score — Inboxrise shows this as a 0–100 score updated daily. A score of 40+ by day 14 is healthy progress.
You can start very small campaigns (under 20 emails/day to warm contacts) during this phase if you need to — but keep total send volume (warmup + campaign) under your daily limit.
Days 15–22: Scaling (30–50 emails/day)
Your reputation is now established enough to absorb a few negative signals without major damage. Continue warmup at 30–40 emails/day while starting cautious campaign sends.
Target score by day 22: 65–75. Below 60 at this point suggests your warmup network isn't engaging properly, or there are authentication issues dragging you down.
Days 23–30: Ready to send (50+ emails/day)
At this point your inbox has a real sender history. A score of 75+ means you can send campaigns at your full daily limit without deliverability risk. 90+ puts you in "excellent" territory — some of the best-performing senders in the Inboxrise network maintain 90+ indefinitely.
The five metrics that tell you if warmup is working
- Reputation score — should increase by at least 5–8 points per week
- Spam rescue rate — how many emails are being rescued from spam. High is good initially; should decrease as reputation builds
- Open rate on warmup emails — target 55–70%
- Reply rate on warmup emails — target 25–35%
- Inbox placement — test weekly using mail-tester.com. Should be 8/10+ by day 14 and 9–10/10 by day 30
Common warmup mistakes
- Sending campaigns too early — score below 70, reputation hasn't stabilised
- Disabling warmup once campaigns start — keep warmup running permanently at a lower volume to maintain your score
- Using a warmup service without authentication — SPF/DKIM/DMARC failures will undermine your warmup progress
- Sending warmup emails that look like templates — warmup networks that send obviously automated emails generate weaker engagement signals
The key insight: Warmup isn't a one-time setup. It's an ongoing infrastructure. The best-performing senders on Inboxrise keep warmup enabled at 20–30 emails/day permanently, maintaining their reputation even during periods when they aren't running active campaigns.